Wait Events
  • V$EVENT_NAME event name
  • V$SESSION_WAIT displays the events for which sessions have just completed waiting or are currently waiting.
  • V$SYSTEM_EVENT displays the total number of times all the sessions have waited for the events in that view.
  • V$SESSION_EVENT is similar to V$SYSTEM_EVENT, but displays all waits for each session.

Overview of Wait Event

oracle wait event overview(zh)

Classes of Wait Events

Classes of Wait Events
Administrative Waits resulting from DBA commands that cause users to wait (for example, an index rebuild).
Application Waits resulting from user application code (for example, lock waits caused by row level locking or explicit lock commands).
Cluster Waits related to Real Application Cluster resources (for example, global cache resources such as 'gc cr block busy'.
Commit This wait class only comprises one wait event - wait for redo log write confirmation after a commit (that is, 'log file sync').
Concurrency Waits for internal database resources (for example, latches).
Configuration Waits caused by inadequate configuration of database or instance resources (for example, undersized log file sizes, shared pool size).
Idle Waits that signify the session is inactive, waiting for work (for example, 'SQL*Net message from client').
Network Waits related to network messaging (for example, 'SQL*Net more data to dblink').
Other Waits which should not typically occur on a system (for example, 'wait for EMON to spawn').
Scheduler Resource Manager related waits (for example, 'resmgr: become active').
System I/O Waits for background process IO (for example, DBWR wait for 'db file parallel write').
User I/O Waits for user IO (for example 'db file sequential read').

Descriptions of Common Wait Event Parameters

Descriptions of Common Wait Event Parameters
block# This is the block number of the block for which Oracle needs to wait. The block number is relative to the start of the file. To find the object to which this block belongs, enter the following SQL statements.
select name, kind
from ext_to_obj_view
where file# = file#
and lowb <= block#
and highb >= block#.
blocks The number of blocks that is being either read from or written to the file. The block size is dependent on the file type: Database files have a block size of DB_BLOCK_SIZE, Logfiles and control files have a block size that is equivalent to the physical block size of the platform.
break? If the value for this parameter equals 0, a reset was sent to the client. A nonzero value indicates that a break was sent to the client.
class The class of the block describes how the contents of the block are used. For example, class 1 represents data block, and class 4 represents segment header.
dba The initials "dba" represents the data block address, which consists of a file number and a block number.
driver id The address of the disconnect function of the driver that is currently being used.
file# The following query returns the name of the database file.
select *
from v$datafile
where file# = file#.
id1 The first identifier (id1) of the enqueue or global lock takes its value from P2 or P2RAW. The meaning of the identifier depends on the name (P1).
id2 The second identifier (id2) of the enqueue or global lock takes its value from P3 or P3RAW. The meaning of the identifier depends on the name (P1).
le The relative index number into V$GC_ELEMENT.
mode The mode is usually stored in the low order bytes of P1 or P1RAW and indicates the mode of the enqueue or global lock request. This parameter has one of the following values.
Table C-1 Lock Mode Values
Mode Value Description
1 Null mode
2 Sub-Share
3 Sub-Exclusive
4 Share
5 Share/Sub-Exclusive
6 Exclusive
Use the following SQL statement to retrieve the name of the lock and the mode of the lock request.
select chr(bitand(p1,-16777216)/16777215)
chr(bitand(p1, 16711680)/65535) "Lock",
bitand(p1, 65535) "Mode"
from v$session_wait
where event = 'DFS enqueue lock acquisition'.
name and type The name or "type" of the enqueue or global lock can be determined by looking at the two high order bytes of P1 or P1RAW. The name is always two characters. Use the following SQL statement to retrieve the lock name.
select chr(bitand(p1,-16777216)/16777215)
chr(bitand(p1,16711680)/65535) "Lock"
from v$session_wait
where event = 'DFS enqueue lock acquisition'.
namespace The name of the object namespace as it is displayed in V$DB_OBJECT_CACHE view.
requests The number of I/Os that are "requested." This differs from the number of blocks in that one request could potentially contain multiple blocks.
session# The number of the inactive session. Use the following SQL statement to find more information about the session.
select *
from v$session
where sid = session#.
waited This is the total amount of time the session has waited for this session to terminate.

Descriptions of Wait Events

Descriptions of Wait Events

This section provides detailed descriptions for those wait events of greatest interest. Where appropriate, pointers are provided to further information elsewhere in Oracle Database documentation. For a complete listing of wait events, in alphabetical order, you can issue the following SQL statement:

SQL> SELECT name FROM V$EVENT_NAME ORDER BY name;

alter system set dispatcher

A session has issued a statement ALTER SYSTEM SET DISPATCHER = string and is waiting for the dispatchers to get started.

Wait Time: The session will wait 1 / 100 of a second and check to see if the new dispatchers have started else the session will wait again
Parameter Description
waited Number of times that the session has waited 1 / 100 of a second

batched allocate scn lock request

A session is waiting on another process to allocate a system change number (SCN). If the foreground timed out waiting on a process to get the SCN, the foreground will get the SCN.

Wait Time: The wait time is 1 second on the assumption that an SCN allocation should normally need much less than that

Parameters: None
BFILE check if exists

The session waits to check if an external large object (LOB) exists.

Wait Time: The total elapsed time for the exists call
Parameter Description
session# See "session#"
waited See "waited"

BFILE check if open

The session waits for an external large object (LOB) to open.

Wait Time: The total elapsed time for the isopen call
Parameter Description
session# See "session#"
waited See "waited"

BFILE closure

The session waits for an external large object (LOB) to close.

Wait Time: The total elapsed time for the close call
Parameter Description
session# See "session#"
waited See "waited"

BFILE get length

The session waits on a call to check the size of an external large object (LOB).

Wait Time: The total elapsed time for the call to check the LOB size
Parameter Description
session# See "session#"
waited See "waited"

BFILE get name object

The session waits on a call to find or generate the external name of a external large object.

Wait Time: The total elapse time for make external file name to complete
Parameter Description
session# See "session#"
waited See "waited"

BFILE get path object

The session is waiting on a call to find or generate the external path name of an external large object (LOB).

Wait Time: The total elapsed time for make external path to complete
Parameter Description
session# See "session#"
waited See "waited"

BFILE internal seek

The session waits for a positioning call within the external large object (LOB) to complete.

Wait Time: The total elapse time for the seek to complete
Parameter Description
session# See "session#"
waited See "waited"

BFILE open

The session waits for an external large object (LOB) to open.

Wait Time: The total elapsed time for the isopen call
Parameter Description
session# See "session#"
waited See "waited"

BFILE read

The session waits for a read from a external large object (LOB) to complete.

Wait Time: The total elapse time for the read to complete
Parameter Description
session# See "session#"
waited See "waited"

broadcast mesg queue transition

Processes enter "wait for broadcast mesg queue transition" when cleaning up a publisher channel handle to a RELIABLE broadcast channel. The publisher is responsible for moving the message to the free queue, but it cannot do so until the message is in the done queue. If the message is still not in the done queue, process enters this wait. This wait event will most likely show up when an Oracle process is about to exit normally, or when PMON cleans up a dead process.

Wait Time: Varies
Parameter Description
channel handle publisher channel handle pointer
message broadcast message pointer
location A number indicating the function in KSR where the process is waiting

broadcast mesg recovery queue transition

Processes enter "wait for broadcast mesg recovery queue transition" when cleaning up a publisher channel handle to a RELIABLE broadcast channel. The broadcasted message is in the recovery queue of another channel handle (for example, ch2). Process enters this wait, if the message is yet to be removed from the recovery queue of the ch2 channel handle. This wait event will most likely show up when an Oracle process is about to exit normally, or when PMON cleans up a dead process.

Wait Time: Varies
Parameter Description
channel handle Publisher channel handle pointer
message Broadcast message pointer
location A number indicating the function in KSR where the process is waiting

buffer busy waits

Wait until a buffer becomes available. This event happens because a buffer is either being read into the buffer cache by another session (and the session is waiting for that read to complete) or the buffer is the buffer cache, but in a incompatible mode (that is, some other session is changing the buffer).

Wait Time: Normal wait time is 1 second. If the session was waiting for a buffer during the last wait, then the next wait will be 3 seconds.
Parameter Description
file# See "file#"
block# See "block#"
id The buffer busy wait event is called from different places in the session

buffer deadlock

Oracle does not really wait on this event; the foreground only yields the CPU. Thus, the chances of catching this event are very low. This is not an application induced deadlock, but an assumed deadlock by the cache layer. The cache layer cannot get a buffer in a certain mode within a certain amount of time.

Wait Time: 0 seconds. The foreground process only yields the CPU and will usually be placed at the end of the CPU run queue.
Parameter Description
class See "class"
mode See "mode"
flag The flag points to the internal flags used by the session to get this block
dba See "dba"

buffer latch

The session waits on the buffer hash chain latch. Primarily used in the dump routines.

Wait Time: 1 second
Parameter Description
latch addr The virtual address in the SGA where this latch is located. Use the following statement to find the name of this latch:

select *
from v$latch a, v$latchname b
where addr = latch addr
and a.latch# = b.latch#;

chain# The index into array of buffer hash chains. When the chain is 0xfffffff, the foreground waits on the LRU latch.

buffer read retry

This event occurs only if the instance is mounted in shared mode (Oracle Real Application Cluster). During the read of the buffer, the contents changed. This means that either:

The version number, dba, or the incarnation and sequence number stored in the block no longer match

The checksum on the block does not match the checksum in the block

The block will be re-read (this may fail up to 3 times), then corruption is assumed and the corrupt block is dumped in the trace file.

Wait Time: The wait time is the elapsed time of the read
Parameter Description
file# See "file#"
block# See "block#"

checkpoint completed

A session waits for a checkpoint to complete. This could happen, for example, during a close database or a local checkpoint.

Wait Time: 5 seconds

Parameters: None
cleanup of aborted processes

When a process spawn is aborted while the process spawning background is in the middle of spawning, the current session must wait until the pid of the new process is filled in. Once the pid is filled in, then the process spawn can be actually aborted.

Wait Time: Usually 3 seconds
Parameter Description
location Location of the wait

control file parallel write

This event occurs while the session is writing physical blocks to all control files. This happens when:

The session starts a control file transaction (to make sure that the control files are up to date in case the session crashes before committing the control file transaction)

The session commits a transaction to a control file

Changing a generic entry in the control file, the new value is being written to all control files

Wait Time: The wait time is the time it takes to finish all writes to all control files
Parameter Description
files The number of control files to which the session is writing
blocks The number of blocks that the session is writing to the control file
requests The number of I/O requests which the session wants to write

control file sequential read

Reading from the control file. This happens in many cases. For example, while:

Making a backup of the control files

Sharing information (between instances) from the control file

Reading other blocks from the control files

Reading the header block

Wait Time: The wait time is the elapsed time of the read
Parameter Description
file# The control file from which the session is reading
block# Block number in the control file from where the session starts to read. The block size is the physical block size of the port (usually 512 bytes, some UNIX ports have 1 or 2 Kilobytes).
blocks The number of blocks that the session is trying to read

control file single write

This wait is signaled while the control file's shared information is written to disk. This is an atomic operation protected by an enqueue (CF), so that only one session at a time can write to the entire database.

Wait Time: The wait time is the elapsed time of the write
Parameter Description
file# This identifies the control file to which the session is currently writing
block# Block number in the control file where the write begins. The block size is the as the physical block size of the port (usually 512 bytes, some UNIX ports have 1 or 2 Kilobytes).
blocks The number of blocks that the session is trying to read

cursor: mutex S

A session waits on this event when it is requesting a mutex in shared mode, when another session is currently holding a this mutex in exclusive mode on the same cursor object.
Parameter Description
P1 Hash value of cursor
P2 Mutex value (top 2 bytes contain SID holding mutex in exclusive mode, and bottom two bytes usually hold the value 0)
P3 Mutex where (an internal code locator) OR'd with Mutex Sleeps

cursor: mutex X

The session requests the mutex for a cursor object in exclusive mode, and it must wait because the resource is busy. The mutex is busy because either the mutex is being held in exclusive mode by another session or the mutex is being held shared by one or more sessions. The existing mutex holder(s) must release the mutex before the mutex can be granted exclusively.
Parameter Description
P1 Hash value of cursor
P2 Mutex value (top 2 bytes contain SID holding mutex in exclusive mode, and bottom two bytes usually hold the value 0)
P3 Mutex where (an internal code locator) OR'd with Mutex Sleeps

cursor: pin S

A session waits on this event when it wants to update a shared mutex pin and another session is currently in the process of updating a shared mutex pin for the same cursor object. This wait event should rarely be seen because a shared mutex pin update is very fast.

Wait Time: Microseconds
Parameter Description
P1 Hash value of cursor
P2 Mutex value (top 2 bytes contains SID holding mutex in exclusive mode, and bottom two bytes usually hold the value 0)
P3 Mutex where (an internal code locator) OR'd with Mutex Sleeps

cursor: pin S wait on X

A session waits for this event when it is requesting a shared mutex pin and another session is holding an exclusive mutex pin on the same cursor object.

Wait Time: Microseconds
Parameter Description
P1 Hash value of cursor
P2 Mutex value (top 2 bytes contains SID holding mutex in exclusive mode, and bottom two bytes usually hold the value 0)
P3 Mutex where (an internal code locator) OR'd with Mutex Sleeps

cursor: pin X

A session waits on this event when it is requesting an exclusive mutex pin for a cursor object and it must wait because the resource is busy. The mutex pin for a cursor object can be busy either because a session is already holding it exclusive, or there are one or more sessions which are holding shared mutex pin(s). The exclusive waiter must wait until all holders of the pin for that cursor object have released it, before it can be granted.

Wait Time: Microseconds
Parameter Description
P1 Hash value of cursor
P2 Mutex value (top 2 bytes contains SID holding mutex in exclusive mode, and bottom two bytes usually hold the value 0)
P3 Mutex where (an internal code locator) OR'd with Mutex Sleeps

Data Guard: process clean up

During Data Guard process termination, Data Guard will wait for one second for process cleanup to complete.
Data Guard: process exit

During Data Guard process termination, Data Guard will wait for a process to exit before attempting any process cleanup that may be required. It will sleep for one second between each check for process exit.
Data Guard Broker: single instance

The Data Guard Broker (DMON) process waits for the other instances in this cluster to complete shutdown before continuing with the broker operation.

Wait Time: Depends on the number of instances, but not exceeding 30 seconds times the number of instances
db file parallel read

This happens during recovery. It can also happen during buffer prefetching, as an optimization (rather than performing multiple single-block reads). Database blocks that need to be changed as part of recovery are read in parallel from the database.

Wait Time: Wait until all of the I/Os are completed
Parameter Description
files This indicates the number of files to which the session is reading
blocks This indicates the total number of blocks to be read
requests This indicates the total number of I/O requests, which will be the same as blocks

db file parallel write

This event occurs in the DBWR. It indicates that the DBWR is performing a parallel write to files and blocks. When the last I/O has gone to disk, the wait ends.

Wait Time: Wait until all of the I/Os are completed
Parameter Description
requests This indicates the total number of I/O requests, which will be the same as blocks
interrupt
timeout This indicates the timeout value in centiseconds to wait for the IO completion.

db file scattered read

Similar to db file sequential read, except that the session is reading multiple data blocks.

Wait Time: The wait time is the actual time it takes to do all of the I/Os
Parameter Description
file# See "file#"
block# See "block#"
blocks The number of blocks that the session is trying to read from the file# starting at block#

db file sequential read

The session waits while a sequential read from the database is performed. This event is also used for rebuilding the control file, dumping datafile headers, and getting the database file headers.

Wait Time: The wait time is the actual time it takes to do the I/O
Parameter Description
file# See "file#"
block# See "block#"
blocks This is the number of blocks that the session is trying to read (should be 1)

db file single write

This event is used to wait for the writing of the file headers.

Wait Time: The wait time is the actual time it takes to do the I/O
Parameter Description
file# See "file#"
block# See "block#"
blocks This is the number of blocks that the session is trying to write in file# starting at block#

DFS db file lock

This event occurs only for the DBWR in the Oracle Real Application Cluster. Each DBWR of every instance holds a global lock on each file in shared mode. The instance that is trying to offline the file will escalate the global lock from shared to exclusive. This signals the other instances to synchronize their SGAs with the control file before the file can be taken offline. The name of this lock is DF (see Appendix D, "Oracle Enqueue Names" for more information).

Wait Time: 1 second in loop. The DBWR is waiting in a loop (sleep, check) for the other instances to downgrade to NULL mode. During this time, the DBWR cannot perform other tasks such as writing buffers.
Parameter Description
file See "file#"

DFS lock handle

The session waits for the lock handle of a global lock request. The lock handle identifies a global lock. With this lock handle, other operations can be performed on this global lock (to identify the global lock in future operations such as conversions or release). The global lock is maintained by the DLM.

Wait Time: The session waits in a loop until it has obtained the lock handle from the DLM. Inside the loop there is a wait of 0.5 seconds.
Parameter Description
name See "name and type"
mode See "mode"
id1 See "id1"
id2 See "id2"

The session needs to get the lock handle.
direct path read

During Direct Path operations the data is asynchronously read from the database files. At some stage the session needs to make sure that all outstanding asynchronous I/O have been completed to disk. This can also happen if during a direct read no more slots are available to store outstanding load requests (a load request could consist of multiple I/Os).

Wait Time: 10 seconds. The session will be posted by the completing asynchronous I/O. It will never wait the entire 10 seconds. The session waits in a tight loop until all outstanding I/Os have completed.
Parameter Description
descriptor address This is a pointer to the I/O context of outstanding direct I/Os on which the session is currently waiting
first dba The dba of the oldest I/O in the context referenced by the descriptor address
block cnt Number of valid buffers in the context referenced by the descriptor address

direct path write

During Direct Path operations, the data is asynchronously written to the database files. At some stage the session needs to make sure that all outstanding asynchronous I/O have been completed to disk. This can also happen if, during a direct write, no more slots are available to store outstanding load requests (a load request could consist of multiple I/Os).

Wait Time: 10 seconds. The session will be posted by the completing asynchronous I/O. It will never wait the entire 10 seconds. The session waits in a tight loop until all outstanding I/Os have completed.
Parameter Description
descriptor address This is a pointer to the I/O context of outstanding direct I/Os on which the session is currently waiting
first dba The dba of the oldest I/O in the context referenced by the descriptor address
block cnt Number of valid buffers in the context referenced by the descriptor address

dispatcher shutdown

During shutdown immediate or normal, the shutdown process must wait for all the dispatchers to shutdown. As each dispatcher is signaled, the session that causes the shutdown is waits on this event until the requested dispatcher is no longer alive.

Wait Time: 1 second
Parameter Description
waited Indicates the cumulative wait time. After 5 minutes, the session writes to the alert and trace files to indicate that there might be a problem.

dispatcher timer

This basically means that the dispatcher is idle and waiting for some work to arrive.

Wait Time: 60 seconds
Parameter Description
sleep time The intended sleep time. The dispatcher will return to work sooner if it is posted by either data arriving on the network or by a post from a shared server process to send data back to the client.

duplicate cluster key

It is possible for a race condition to occur when creating a new cluster key. If it is found that another process has put the cluster key into the data/index block, then the session waits and retries. The retry should then find a valid cluster key.

Wait Time: 0.01 seconds
Parameter Description
dba The dba of the block into which the session is trying to insert a cluster key

enq: OW - initialization

A session will wait on this event if it is trying to initialize the database wallet, and another session has already begun an initialization.

Wait Time: Total time necessary to initialize the wallet context

Parameters: None
enq: OW - termination

A session will wait on this event if it is trying to terminate the database wallet, and another session has already begun a termination.

Wait Time: Total time necessary to deallocate memory used by the wallet context and terminate the context.

Parameters: None
enqueue

The session is waiting for a local enqueue. The wait is dependent on the name of the enqueue (see Appendix D, "Oracle Enqueue Names").

Wait Time: Depends on the enqueue name
Parameter Description
name See "name and type"
mode See "mode"

flashback buf free by RVWR

This wait event only occurs when Flashback Database is turned on. A session waits for recovery writer (RVWR) to write flashback data to the flashback logs on disk because the buffers are full. Until RVWR can free up the buffers, the session may need to wait.

If this event becomes a top wait event for the database, it is typically because the file system or storage system for the Flash Recovery Area does not support enough bandwidth for Oracle to write the flashback database logs. Refer to the Flashback Database section in Oracle Database Backup and Recovery Basics for tuning considerations.

Wait Time: 1 second

Parameters: None
free buffer waits

This will happen if:

All buffer gets have been suspended. This could happen when a file was read-only and is now read-write. All the existing buffers need to be invalidated since they are not linked to lock elements (needed when mounted parallel (shared)). So cache buffers are not assigned to data block addresses until the invalidation is finished.

The session moved some dirty buffers to the dirty queue and now this dirty queue is full. The dirty queue needs to be written first. The session will wait on this event and try again to find a free buffer

This also happens after inspecting free buffer inspected buffers. If no free buffer is found, Oracle waits for one second, and then tries to get the buffer again (depends on the context). For more information, see free buffer inspected.

Wait Time: 1 second
Parameter Description
file# See "file#"
block# See "block#"

free global transaction table entry

The session is waiting for a free slot in the global transaction table (used by the Distributed Database option). It will wait for 1 second and try again.

Wait Time: 1 second
Parameter Description
tries The number of times the session tried to find a free slot in the global transaction table

free process state object

Used during the creation of a process. The session will scan the process table and look for a free process slot. If none can be found, PMON is posted to check if all the processes currently in the process table are still alive. If there are dead processes, then PMON will clean them and make the process slot available to new processes. The waiting process will then rescan the process table to find the new slot.

Wait Time: 1 second

Parameters: None
GCS lock open S

The session waits for a resource get in SHARED mode on the block identified by file# and block#.

Wait Time: 1 second
Parameter Description
file# See "file#"
block# See "block#"
class See "class"

GCS lock open X

The session waits for a resource get in EXCLUSIVE mode on the block identified by file# and block#.

Wait Time: 1 second
Parameter Description
file# See "file#"
block# See "block#"
lenum See "le"

gcs remastering wait for drop pkey

A session dropping an object waits on the lock manager daemon (LMD) to remove the object's affinity to an instance.

Wait Time: 20 centi-seconds
Parameter Description
pkey The object id of the database object being dropped

global cache busy

The session waits to convert a buffer from Shared Current to Exclusive Current status.

Wait Time: 1 second
Parameter Description
file# See "file#"
block# See "block#"
le See "lenum" on page A-8

global cache lock cleanup

PMON is waiting for an LCK process to cleanup the lock context after a foreground process died while doing a global cache lock operation.

Wait Time: 1 second
Parameter Description
file# See "file#"
block# See "block#"
lenum See "lenum" on page A-8

global cache freelist

All releasable locks are used and a new one has been requested. To make a resource element available, a resource element is pinged.

Wait Time: The duration of the resource get operation to ping the resource element

Parameters: None
inactive session

This event is used for two purposes:

Switching sessions

If a time-out period has been specified, then wait that amount of time for the session to be detached.

Killing sessions

From either KILL SESSION or internal request. Having posted a session that it should kill itself, wait for up to 1 minute for the session to terminate.

Wait Time: 1 second
Parameter Description
session# See "session#"
waited See "waited"

inactive transaction branch

The session waits for a transaction branch that is currently used by another session.

Wait Time: 1 second
Parameter Description
branch# The serial number of the transaction for which the session is waiting
waited See "waited"

index block split

While trying to find an index key in an index block, Oracle noticed that the index block was being split. Oracle will wait for the split to finish and try to find the key again.

Wait Time: The session will yield the CPU, so there is no actual waiting time
Parameter Description
rootdba The root of the index
level This is the level of the block that the session is trying to split in the index. The leaf blocks are level 0. If the level is > 0, it is a branch block. (The root block can be considered a special branch block).
childdba The block that the session is trying to split

instance state change

The session waits for SMON to enable or disable cache or transaction recovery. This usually happens during ALTER DATABASE OPEN or CLOSE.

Wait Time: Wait time depends on the amount of time the action takes (that is, the amount of recovery needed)
Parameter Description
layer This value can be 1 or 2. If 1, it means that the transaction layer wants transaction recovery to be performed. If 2, it means that cache recovery will be performed.
value This value can be 0 (disable) or 1 (enable)
waited The number of seconds waited so far

io done

The session waits for an I/O to complete or it waits for a slave process to become available to submit the I/O request. This event occurs on platforms that do not support asynchronous I/O.

Wait Time: 50 milliseconds
Parameter Description
msg ptr A pointer to the I/O request

kcl bg acks

The session waits for the background LCK process(es) to finish what they are doing. For example:

Lock recovery

Initializing the locks (start up)

Finalizing the locks (shut down)

Wait Time: 10 seconds
Parameter Description
count The number of LCK processes that have finished
loops The number times the process had to wait for the LCK processes to finish what they were doing

ksxr wait for mount shared

The cross instance broadcast facility of this Oracle instance is waiting for the database mount in shared mode to complete.

Wait Time: The time taken for the instance to mount. An indefinite wait on this event implies that the instance startup is hanging.
ktm: instance recovery

The session waits for SMON to finish the instance, transaction recovery, or sort segment cleanup.

Wait Time: The wait time can vary and depends on the amount of recovery needed
Parameter Description
undo segment# If the value is 0, SMON is probably performing instance recovery. If P1 > 0, use this query to find the undo segment:

select *
from v$rollstat
where usn = undo segment#;

latch activity

This event is used as part of the process of determining whether a latch needs to be cleaned.

Wait Time: 0.05 to 0.1 seconds
Parameter Description
address The address of the latch that is being checked
number The latch number of the latch that has activity. To find more information on the latch, use the following SQL statement:

select *
from v$latchname
where latch# = number;

process# If this is 0, it is the first phase of the in-flux tests

latch free

The process waits for a latch that is currently busy (held by another process).

Wait Time: The wait time increases exponentially and does not include spinning on the latch (active waiting). The maximum wait time also depends on the number of latches that the process is holding. There is an incremental wait of up to 2 seconds.
Parameter Description
address The address of the latch for which the process is waiting
number The latch number that indexes in the V$LATCHNAME view.To find more information on the latch, use the following SQL statement:

select *
from v$latchname
where latch# = number;

tries A count of the number of times the process tried to get the latch (slow with spinning) and the process has to sleep

library cache load lock

The session tries to find the load lock for the database object so that it can load the object. The load lock is always obtained in Exclusive mode, so that no other process can load the same object. If the load lock is busy the session will wait on this event until the lock becomes available.

Wait Time: 3 seconds (1 second for PMON)
Parameter Description
object address Address of the object being loaded
lock address Address of load lock being used
mask Indicates which data pieces of the object that needs to be loaded

library cache lock

This event controls the concurrency between clients of the library cache. It acquires a lock on the object handle so that either:

One client can prevent other clients from accessing the same object

The client can maintain a dependency for a long time (for example, no other client can change the object)

This lock is also obtained to locate an object in the library cache.

Wait Time: 3 seconds (1 second for PMON)
Parameter Description
handle address Address of the object being loaded
lock address Address of the load lock being used. This is not the same thing as a latch or an enqueue, it is a State Object.
mode Indicates the data pieces of the object which need to be loaded
namespace See "namespace"

library cache pin

This event manages library cache concurrency. Pinning an object causes the heaps to be loaded into memory. If a client wants to modify or examine the object, the client must acquire a pin after the lock.

Wait Time: 3 seconds (1 second for PMON)
Parameter Description
handle address Address of the object being loaded
pin address Address of the load lock being used. This is not the same thing as a latch or an enqueue, it is basically a State Object.
mode Indicates which data pieces of the object that needs to be loaded
namespace See "namespace"

library cache shutdown

The process shutting down the instance waits for sessions to complete before proceeding with library cache shutdown.
LMON global data update

The rolling migration operation is waiting for a response from LMON to acknowledge the global data was updated.

Wait Time: The time it takes for LMON to publish/retrieve the global data associated with a

Parameters: None
lock manager wait for remote message

The lock manager waits for a message from a remote lock manager in the same configuration.

Wait Time: The elapsed time of the wait
Parameter Description
waittime The elapsed time of the actual wait

log buffer space

Waiting for space in the log buffer because the session is writing data into the log buffer faster than LGWR can write it out. Consider making the log buffer bigger if it is small, or moving the log files to faster disks such as striped disks.

Wait Time: Usually 1 second, but 5 seconds if it is waiting for a Switch Logfile to complete

Parameters: None
log file parallel write

Writing redo records to the redo log files from the log buffer.

Wait Time: Time it takes for the I/Os to complete. Even though redo records are written in parallel, the parallel write is not complete until the last I/O is on disk.
Parameter Description
files Number of files to be written
blocks Number of blocks to be written
requests Number of I/O requests

log file sequential read

Waiting for the read from this logfile to return. This is used to read redo records from the log file.

Wait Time: Time it takes to complete the physical I/O (read)
Parameter Description
log# The relative sequence number of the logfiles within a log group (used only when dumping the logfiles)
block# See "block#"
blocks The number of blocks to read

log file single write

Waiting for the write to this logfile to complete. This event is used while updating the header of the logfile. It is signaled when adding a log file member and when incrementing sequence numbers.

Wait Time: Time it takes for the physical I/O (write) to complete
Parameter Description
log# This is the number of the group/log to which the session is currently writing
block# See "block#"
blocks The number of blocks to write

log file switch (archiving needed)

Waiting for a log switch because the log that the LGWR will be switching into has not been archived yet. Check the alert file to make sure that archiving has not stopped due to a failed archive write. To speed archiving, consider adding more archive processes or putting the archive files on striped disks.

Wait Time: 1 second

Parameters: None
log file switch (checkpoint incomplete)

Waiting for a log switch because the session cannot wrap into the next log. Wrapping cannot be performed because the checkpoint for that log has not completed.

Wait Time: 1 second

Parameters: None
log file switch (clearing log file)

Waiting for a log switch because the log is being cleared due to a CLEAR LOGFILE command or implicit clear logfile executed by recovery.

Wait Time: 1 second

Parameters: None
log file switch (private strand flush incomplete)

User sessions trying to generate redo, wait on this event when LGWR waits for DBWR to complete flushing redo from IMU buffers into the log buffer; when DBWR is complete LGWR can then finish writing the current log, and then switch log files.

Wait Time: 1 second

Parameters: None
log file switch completion

Waiting for a log switch to complete.

Wait Time: 1 second

Parameters: None
log file sync

When a user session commits, the session's redo information needs to be flushed to the redo logfile. The user session will post the LGWR to write the log buffer to the redo log file. When the LGWR has finished writing, it will post the user session.

Wait Time: The wait time includes the writing of the log buffer and the post.
Parameter Description
buffer# The number of the physical buffer in the redo log buffer that needs to be synchronized

log switch/archive

Used as part of the ALTER SYSTEM ARCHIVE LOG CHANGE scn statement. The session waits for the current log from all open threads to be archived.

Wait Time: Wait for up to 10 seconds
Parameter Description
thread# The thread number of the thread that is currently archiving its current log

optimizer stats update retry

When concurrent sessions try to update optimizer statistics for the same object, all of them except the one that successfully acquired all necessary locks/pins on the library/row cache entries, wait on this wait event and then retry locking after a short period of time. In addition to explicit statistics gathering and maintenance operations using the DBMS_STATS package, Oracle database itself may try to update statistics for some objects, either on behalf of the user or for its own maintenance purposes.

Wait Time: 10 ms

Parameters: None
pending global transaction(s)

This event should happen only during testing. The session waits for pending transactions to clear.

Wait Time: 30 seconds
Parameter Description
scans Number of times the session has scanned the PENDING_TRANS$ table

pipe get

The session waits for a message to be received on the pipe or for the pipe timer to expire.

Wait Time: There is a 5 second wake up (check) and the pipe timer set by the user
Parameter Description
handle address The library cache object handle for this pipe
buffer length The length of the buffer
timeout The pipe timer set by the user

pipe put

The session waits for the pipe send timer to expire or for space to be made available in the pipe.

Wait Time: There is the 5 second wakeup (check) and the user-supplied timeout value
Parameter Description
handle address The library cache object handle for this pipe
record length The length of the record or buffer that has been put into the pipe
timeout The pipe timer set by the user

PL/SQL lock timer

This event is called through the DBMSLOCK.SLEEP procedure or USERLOCK.SLEEP procedure. This event will most likely originate from procedures written by a user.

Wait Time: The wait time is in hundredths of seconds and is dependent on the user context
Parameter Description
duration The duration that the user specified in the DBMS_LOCK.SLEEP or USER_LOCK.SLEEP procedures

pmon timer

This is the main wait event for PMON. When PMON is idle, it is waiting on this event.

Wait Time: Up to 3 seconds, if not posted before
Parameter Description
duration The actual amount of time that the PMON is trying to sleep

prewarm transfer retry

Release a hash latch, then wait under this event before attempting to re-acquire the hash latch.

Wait Time: 10ms

Parameters: None
prior process spawner to be cleaned up

When a prior process has died while spawning a background, the current process which is trying to spawn new a background must wait until the prior process state is cleaned up.

Wait Time: Usually 3 - 10 seconds
Parameter Description
process_pid process identifier (see V$PROCESS.PID) of the process whose state needs to be cleaned up.
process_sno process serial number (see V$PROCESS.SERIAL#) of the process whose state needs to be cleaned up.

process startup

Wait for a shared server, Dispatcher, or other background process to start.

Wait Time: Wait up to 1 second for a background process to start. If timed out, then re-wait until 5 minutes have passed and signal an error. If the process has started, the event will acknowledge this.
Parameter Description
type The process type that was started
process# The process number of the process being started
waited Cumulative time waited for the process to start

PX Deque wait

The process is waiting for a message during a parallel execute.

Wait Time: The wait time depends on how quickly the message arrives. Wait times can vary, but it will normally be a short period of time.
Parameter Description
reason The reason for dequeuing
sleeptime The amount of time that the session slept
loop The total number of times that the session has slept

PX qref latch

Each parallel execution process has a parallel execution qref latch, which needs to be acquired before the queue buffers can be manipulated.

Wait Time: Wait up to 1 second
Parameter Description
function Indicates the type of wait that the session is doing
sleeptime The amount of time that the session waits (in hundredths of a second)
qref The address of the process queue for which the session is waits

PX server shutdown

During normal or immediate shutdown the parallel execution slaves are posted to shutdown cleanly. If any parallel execution slaves are still alive after 10 seconds, they are killed.

Wait Time: Wait up to 0.5 seconds
Parameter Description
nalive The number of parallel execution slaves that are still running
sleeptime The total sleeptime since the session started to wait on this event
loop The number of times the session waited for this event

PX signal server

This event occurs only in Exclusive mode. The query coordinator is signalling the Query Slaves that an error has occurred.

Wait Time: 0.5 seconds
Parameter Description
serial The serial number of the slave process queue
error The error that has occurred
nbusy The number of slave processes that are still busy

Streams AQ: waiting for messages in the queue

The session is waiting on an empty OLTP queue (Advanced Queuing) for a message to arrive so that the session can dequeue that message.

Wait Time: The amount of time that the session wants to wait is determined by the parameter wait time
Parameter Description
queue id The ID of the OLTP queue for which this session is waiting
process# The process number of the process in which this session runs
wait time The intended wait time for this session

rdbms ipc message

The background processes (LGWR, DBWR, LMS0) use this event to indicate that they are idle and are waiting for the foreground processes to send them an IPC message to do some work.

Wait Time: Up to 3 seconds. The parameter timeout shows the true sleep time.
Parameter Description
timeout The amount of time that the session waits for an IPC message

rdbms ipc message block

This event indicates that all message blocks are in use and that the session had to wait for a message block to become available.

Wait Time: Wait up to 60 seconds

Parameters: None
rdbms ipc reply

This event is used to wait for a reply from one of the background processes.

Wait Time: The wait time is specified by the user and is indicated by the parameter timeout.
Parameter Description
from_process The background process for which the session is waiting. The wait is for a reply to an IPC message sent by the session.
timeout The amount of time in seconds that this process will wait for a reply

read by other session

This event occurs when a session requests a buffer that is currently being read into the buffer cache by another session. Prior to release 10.1, waits for this event were grouped with the other reasons for waiting for buffers under the 'buffer busy wait' event

Wait Time: Time waited for the buffer to be read by the other session (in microseconds)
Parameter Description
file# See "file#"
block# See "block#"
class# See "class"

resmgr: become active

The session is waiting for a resource manager active session slot. This event occurs when the resource manager is enabled and the number of active sessions in the session's current consumer group exceeds the current resource plan's active session limit for the consumer group. To reduce the occurrence of this wait event, increase the active session limit for the session's current consumer group.

Wait Time: The time the session waited to be allocated an active session slot
Parameter Description
location location of the wait

resmgr: cpu quantum

The session is waiting to be allocated a quantum of cpu. This event occurs when the resource manager is enabled and is throttling CPU consumption. To reduce the occurrence of this wait event, increase the CPU allocation for the sessions's current consumer group.

Wait Time: The time the session waited to acquire a CPU quantum
Parameter Description
location Location of the wait

rolling migration: cluster quisce

This is the wait event that instances wait on when cluster is about to start a rolling migration. The instances are waiting for any privileged operations that blocks rolling migration to complete before allowing rolling migration.

Wait Time: 1 second
Parameter Description
location Its value will be 1 if the wait is for completion of the privileged operations so that a rolling upgrade/downgrade can start. Its value will be 2 if the wait is for completion of the rolling upgrade/downgrade on all the nodes in the cluster.
waits The number of seconds spent waiting at the current location.

row cache lock

The session is trying to get a data dictionary lock.

Wait Time: Wait up to 60 seconds.
Parameter Description
cache id The CACHE# column value in the V$ROWCACHE view
mode See "mode"
request The pipe timer set by the user

sbtbufinfo

This function is called when Oracle needs to discover the size, and number, of I/O buffers that have been allocated by the SBT layer. It should be very fast and never block.

Wait Time: Less than one millisecond

Parameters: None
sbtgetbuf

This function obtains one I/O buffer that Oracle will use for I/O during a backup job.

Wait Time: Less than one millisecond

Parameters: None
sbtmapbuf

This is an internal function used to facilitate multi-process buffer management. It should be very fast and never block.

Wait Time: Less than one millisecond

Parameters: None
sbtrelbuf

This function releases an I/O buffer that has been already processed during a restore job, so that the SBT layer can fill it with more data. It should be very fast and never block.

Wait Time: Less than one millisecond

Parameters: None
scginq AST call

Called by the session to find the highest lock mode that is held on a resource.

Wait Time: Wait up to 0.2 seconds, but the wait will continue until the NULL mode Acquisition AST has fired.

Parameters: None
SGA: allocation forcing component growth

Process waiting on an immediate mode memory transfer with auto-tune SGA after a 4031 for MMAN to get the memory and post it.

Wait Time: 10 msec

Parameters: None
SGA: MMAN sleep for component shrink

MMAN to wait and post itself for satisfying an auto-tuned memory request while trying to fully free a component's quiesced granules. In Release 10.1, the name of this event was 'wait for SGA component shrink'.

Wait Time: 10 msec
Parameter Description
P1 component_id (corresponding to the memory pool)
P2 Current size in granules
P3 Target size in granules

SGA: sga_target resize

Memory resize requests wait while sga target is being resized.In Release 10.1, the name of this event was 'wait for sga_target resize'.

Wait Time: 10 msec

Parameters: None
single-task message

When running single task, this event indicates that the session waits for the client side of the executable.

Wait Time: Total elapsed time that this session spent in the user application

Parameters: None
smon timer

This is the main idle event for SMON. SMON will be waiting on this event most of the time until it times out or is posted by another process.

Wait Time: 5 minutes (300 seconds)
Parameter Description
sleeptime The amount of time that SMON tries to wait on this event in seconds
failed The number of times SMON was posted when there some kind of error

SQL*Net break/reset to client

The server sends a break or reset message to the client. The session running on the server waits for a reply from the client.

Wait Time: The actual time it takes for the break or reset message to return from the client
Parameter Description
driver id See "driver id"
break? See "break?"

SQL*Net break/reset to dblink

Same as SQL*Net break/reset to client, but in this case, the break/reset message is sent to another server process over a database link.

Wait Time: The actual time it takes for the break or reset message to return from the other server process
Parameter Description
driver id See "driver id"
break? See "break?"

SQL*Net message from client

The server process (foreground process) waits for a message from the client process to arrive.

Wait Time: The time it took for a message to arrive from the client since the last message was sent to the client
Parameter Description
driver id See "driver id"
#bytes The number of bytes received by the server (foreground process) from the client.

SQL*Net message from dblink

The session waits while the server process (foreground process) receives messages over a database link from another server process.

Wait Time: The time it took for a message to arrive from another server (foreground process) since a message was sent to the other foreground process.
Parameter Description
driver id See "driver id"
#bytes The number of bytes received by the server (foreground process) from another foreground process over a database link.

SQL*Net message to client

The server (foreground process) is sending a message to the client.

Wait Time: The actual time the send takes
Parameter Description
driver id See "driver id"
#bytes The number of bytes sent by the server process to the client

SQL*Net message to dblink

The server process (foreground process) is sending a message over a database link to another server process.

Wait Time: The actual time the send takes
Parameter Description
driver id See "driver id"
#bytes The number of bytes sent by the server process to another server process over a database link

SQL*Net more data from client

The server is performing another send to the client. The previous operation was also a send to the client.

Wait Time: The time waited depends on the time it took to receive the data (including the waiting time)
Parameter Description
driver id See "driver id"
#bytes The number of bytes received from the client

SQL*Net more data from dblink

The foreground process is expecting more data from a data base link.

Wait Time: The total time it takes to read the data from the database link (including the waiting time for the data to arrive)
Parameter Description
driver id See "driver id"
#bytes The number of bytes received

SQL*Net more data to client

The server process is sending more data/messages to the client. The previous operation to the client was also a send.

Wait Time: The actual time it took for the send to complete
Parameter Description
driver id See "driver id"
#bytes The number of bytes that are being sent to the client

SQL*Net more data to dblink

The event indicates that the server is sending data over a database link again. The previous operation over this database link was also a send.

Wait Time: The actual time it takes to send the data to the other server
Parameter Description
driver id See "driver id"
#bytes The number of bytes that are sent over the database link to the other server process

switch logfile command

The session waits on the user command SWITCH LOGFILE to complete.

Wait Time: 5 seconds

Parameters: None
timer in sksawat

The session waits for the Archiver (ARCH) asynchronous I/O to complete.

Wait Time: 0.01 seconds

Parameters: None
transaction

Wait for a blocking transaction to be rolled back. Continue waiting until the transaction has been rolled back.

Wait Time: 1 second
Parameter Description
undo seg# The rollback segment ID
slot# The slot ID inside the rollback segment
wrap# The sequence number that is incremented for each transaction
count The number of times that the session has waited on this transaction

unbound tx

The session waits to see if there are any transactions that have been started but do not have a Rollback Segment associated with them.

Wait Time: 1 second

Parameters: None
undo_retention publish retry

This wait can occur for two reasons. A session issuing an ALTER SYSTEM SET UNDO_RETENTION may wait on this event wait while a cluster reconfiguration takes place. Or the background process MMNL may wait for cluster reconfiguration while attempting to determine the max UNDO_RETENTION.

Wait time: 1 second
Parameter Description
P1 Identifies where the retry is happening. Id = 1 retry while publishing into the max undo_retention namespace. Id = 2 retry while iterator accessing the max undo_retention namespace
P2 Retry count (maximum number of retries is 5)

undo segment extension

The undo segment is being extended or shrunk. The session must wait until the operation on the undo segment has finished.

Wait Time: 0.01 seconds
Parameter Description
segment# The ID of the rollback segment that is being extended or shrunk

undo segment recovery

PMON is rolling back a dead transaction. The wait continues until rollback finishes.

Wait Time: 3 seconds
Parameter Description
segment# The ID of the rollback segment that contains the transaction that is being rolled back
tx flags The transaction flags (options) set for the transaction that is being rolled back

undo segment tx slot

Wait for a transaction slot to become available within the selected rollback segment. Continue waiting until the slot is available.

Wait Time: 1 second
Parameter Description
segment# The ID of the rollback segment that contains the transaction that is being rolled back

virtual circuit status

The session waits for a virtual circuit to return a message type indicated by status.

Wait Time: 30 seconds
Parameter Description
circuit# Indicates the virtual circuit# being waited on
status Indicates what the session is waiting for

WMON goes to sleep

WMON is the UNIX-specific Wait Monitor, that can be used to reduce the number of system calls related to setting timers for posting or waiting in Oracle. You need to set an initialization parameter that enables the WMON process.

Wait Time: Depends on the next timeout

Parameters: None
write complete waits

The session waits for a buffer to be written. The write is caused by normal aging or by a cross-instance call.

Wait Time: 1 second
Parameter Description
file# The rollback segment id that contains the transaction that is being rolled back
block# The transaction flags (options) set for the transaction that is being rolled back
id Identifies the reason for waiting

writes stopped by instance recovery or database suspension

The session is blocked until the instance that started Instance Recovery is finished.

Wait Time: 5 seconds
Parameter Description
bythread# The rollback segment id that contains the transaction that is being rolled back
ourthread# The current instance thread number

example on 10.2.0.4:

select event from v$system_event;
 
EVENT
----------------------------------------------------------------
select * from v$system_event;
 
EVENT                                                            TOTAL_WAITS TOTAL_TIMEOUTS TIME_WAITED AVERAGE_WAIT TIME_WAITED_MICRO   EVENT_ID
---------------------------------------------------------------- ----------- -------------- ----------- ------------ ----------------- ----------
WAIT_CLASS_ID WAIT_CLASS# WAIT_CLASS
------------- ----------- ----------------------------------------------------------------
pmon timer                                                           1979807        1977447   576417963       291.15        5.7642E+12 3539483025
   2723168908           6 Idle
 
rdbms ipc message                                                   23182814       18887866  6160046514       265.72        6.1600E+13  866018717
   2723168908           6 Idle
 
Data file init write                                                  107370              0      223245         2.08        2232445229 2326919048
   1740759767           8 User I/O
 
Log archive I/O                                                       625459              0     3991971         6.38        3.9920E+10 2089793129
   4108307767           9 System I/O
 
RMAN backup & recovery I/O                                           4362836              0    10930898         2.51        1.0931E+11 3107297351
   4108307767           9 System I/O
 
class slave wait                                                        3514              0          67          .02            667653 1055154682
   2723168908           6 Idle
 
os thread startup                                                       3917              1       13956         3.56         139558850   86156091
   3875070507           4 Concurrency
 
control file sequential read                                        15974321              0     2488415          .16        2.4884E+10 3213517201
   4108307767           9 System I/O
 
control file single write                                               4320              0       12802         2.96         128021079 2383414886
   4108307767           9 System I/O
 
control file parallel write                                          2582469              0     7363021         2.85        7.3630E+10 4078387448
   4108307767           9 System I/O
 
latch: cache buffers chains                                           138297              0         562            0           5616211 2779959231
   3875070507           4 Concurrency
 
local write wait                                                        3525              0        6133         1.74          61331169 1570123276
   1740759767           8 User I/O
 
write complete waits                                                       1              0           2         1.88             18793 4229542060
   3290255840           2 Configuration
 
buffer busy waits                                                    2004554             41       26263          .01         262634090 2161531084
   3875070507           4 Concurrency
 
read by other session                                                2421191             39     1291935          .53        1.2919E+10 3056446529
   1740759767           8 User I/O
 
enq: RO - fast object reuse                                              568              0         654         1.15           6536026  143262751
   4217450380           1 Application
 
enq: KO - fast object checkpoint                                           3              0          92        30.83            924945 4205197519
   4217450380           1 Application
 
log file sequential read                                              678604              0     1182615         1.74        1.1826E+10  549236675
   4108307767           9 System I/O
 
log file single write                                                  27638              0       22488          .81         224876905  215477332
   4108307767           9 System I/O
 
log file parallel write                                             10306225              0    14006529         1.36        1.4007E+11 3999721902
   4108307767           9 System I/O
 
latch: redo writing                                                       26              0           1          .06             14889 2539661515
   3290255840           2 Configuration
 
log buffer space                                                        5233              4       29339         5.61         293394273 3357856061
   3290255840           2 Configuration
 
log file switch (checkpoint incomplete)                                 3353            938      156547        46.69        1565469427 2867289651
   3290255840           2 Configuration
 
log file switch (private strand flush incomplete)                          2              0          21        10.26            205286  114164561
   3290255840           2 Configuration
 
log file switch (archiving needed)                                       180             98       13014         72.3         130135560  681532028
   3290255840           2 Configuration
 
switch logfile command                                                   288              0        4886        16.97          48863368 3845123846
   4166625743           3 Administrative
 
log file switch completion                                             21825            605      452494        20.73        4524942214 3834950329
   3290255840           2 Configuration
 
log file sync                                                         675497              9      987901         1.46        9879012145 1328744198
   3386400367           5 Commit
 
db file sequential read                                            173658133              0    79344944          .46        7.9345E+11 2652584166
   1740759767           8 User I/O
 
db file scattered read                                              26039614              0    28703125          1.1        2.8703E+11  506183215
   1740759767           8 User I/O
 
db file single write                                                   50934              0       64611         1.27         646108463 1307477558
   1740759767           8 User I/O
 
db file parallel write                                              20267661              0     9921298          .49        9.9213E+10 1620694733
   4108307767           9 System I/O
 
db file parallel read                                                 115994              0      133568         1.15        1335684212  834992820
   1740759767           8 User I/O
 
direct path read                                                     4826228              0      656732          .14        6567323410 3926164927
   1740759767           8 User I/O
 
direct path read temp                                                2100343              0     1048192           .5        1.0482E+10  861319509
   1740759767           8 User I/O
 
direct path write                                                    1094029              0      229488          .21        2294878293  885859547
   1740759767           8 User I/O
 
direct path write temp                                               1285243              0      767615           .6        7676149406   38438084
   1740759767           8 User I/O
 
enq: TM - contention                                                     470            448      134628       286.44        1346283152  668627480
   4217450380           1 Application
 
enq: HW - contention                                                      47              0         215         4.58           2150362 1645217925
   3290255840           2 Configuration
 
undo segment extension                                                151454         151244          56            0            556830 1781586680
   3290255840           2 Configuration
 
enq: TX - row lock contention                                           2773           2669      790754       285.16        7907543279  310662678
   4217450380           1 Application
 
enq: TX - allocate ITL entry                                               4              0           8         2.02             80654  281768874
   3290255840           2 Configuration
 
enq: TX - index contention                                               167              0         242         1.45           2418372 1035026728
   3875070507           4 Concurrency
 
smon timer                                                             23901          18815   555575760     23244.88        5.5558E+12 1403232821
   2723168908           6 Idle
 
PX Deq: Txn Recovery Start                                            193418            311     1787077         9.24        1.7871E+10 1817260038
   2723168908           6 Idle
 
latch: In memory undo latch                                             4272              0          17            0            169945 1394127552
   3875070507           4 Concurrency
 
enq: SQ - contention                                                       9              0           0          .02              1590 2322460838
   3290255840           2 Configuration
 
latch: row cache objects                                               27064              0         592          .02           5919032 1117386924
   3875070507           4 Concurrency
 
row cache lock                                                            83             15        4904        59.08          49035783 1714089451
   3875070507           4 Concurrency
 
cursor: mutex X                                                         8360              0           1            0             12556  877525844
   3875070507           4 Concurrency
 
cursor: mutex S                                                         5735              0           1            0              8406 1575214430
   3875070507           4 Concurrency
 
cursor: pin S wait on X                                                 4385           4369        4704         1.07          47036802 1729366244
   3875070507           4 Concurrency
 
latch: shared pool                                                      1034              0       16782        16.23         167819945 2696347763
   3875070507           4 Concurrency
 
latch: library cache                                                     288              2        2828         9.82          28280583  589947255
   3875070507           4 Concurrency
 
latch: library cache lock                                                652              0        3841         5.89          38414477 2032051689
   3875070507           4 Concurrency
 
library cache pin                                                         88             87       25510       289.89         255102066 2802704141
   3875070507           4 Concurrency
 
library cache load lock                                                   29              0         111         3.81           1106344 2952162927
   3875070507           4 Concurrency
 
TCP Socket (KGAS)                                                     842652              0      100897          .12        1008974107 3680756349
   2000153315           7 Network
 
jobq slave wait                                                         4445           4420     1295127       291.37        1.2951E+10  782339817
   2723168908           6 Idle
 
PX Idle Wait                                                           19918          19098     3753042       188.42        3.7530E+10 3382828453
   2723168908           6 Idle
 
PX Deq: Join ACK                                                         401              0         127          .32           1271447 4205438796
   2723168908           6 Idle
 
PX Deq Credit: need buffer                                            902994              1       15992          .02         159918213 2267953574
   2723168908           6 Idle
 
PX Deq: Msg Fragment                                                      13              0          65            5            650313   77145095
   2723168908           6 Idle
 
PX Deq: Parse Reply                                                       17              0           7          .41             69488 4255662421
   2723168908           6 Idle
 
PX Deq: Execute Reply                                                   1316            838      196303       149.17        1963034804 2599037852
   2723168908           6 Idle
 
PX Deq: Execution Msg                                                   3210           2482      487928          152        4879276467   98582416
   2723168908           6 Idle
 
PX Deq: Table Q Normal                                              10503064             73      653517          .06        6535169519  799271425
   2723168908           6 Idle
 
PX Deq: Table Q Sample                                                   156            150       29880       191.54         298798659 1062854067
   2723168908           6 Idle
 
single-task message                                                      997              0        2902         2.91          29024560 2254800293
   2723168908           6 Idle
 
SQL*Net message to client                                           14097910              0        1532            0          15322927 2067390145
   2000153315           7 Network
 
SQL*Net message to dblink                                           94913830              0       10906            0         109062866 3655533736
   2000153315           7 Network
 
SQL*Net more data to client                                          9367062              0       59352          .01         593518320  554161347
   2000153315           7 Network
 
SQL*Net more data to dblink                                           223023              0        2514          .01          25142857 1958556342
   2000153315           7 Network
 
SQL*Net message from client                                         14097725              0  1599329552       113.45        1.5993E+13 1421975091
   2723168908           6 Idle
 
SQL*Net more data from client                                        2779085              0        9626            0          96255197 3530226808
   2000153315           7 Network
 
SQL*Net message from dblink                                         94913802              0    12115871          .13        1.2116E+11 4093028837
   2723168908           6 Idle
 
SQL*Net more data from dblink                                       70869806              0     1455370          .02        1.4554E+10 1136294303
   2000153315           7 Network
 
SQL*Net break/reset to client                                           8454              0      342579        40.52        3425789966 1963888671
   4217450380           1 Application
 
SQL*Net break/reset to dblink                                            154              0          47           .3            467369  634664853
   4217450380           1 Application
 
PL/SQL lock timer                                                         64             63        6159        96.24          61590868  818280116
   2723168908           6 Idle
 
Streams AQ: waiting for time management or cleanup tasks                3479           3336   301413660     86638.02        3.0141E+12 3702640206
   2723168908           6 Idle
 
Streams AQ: qmn coordinator idle wait                                 422918         212157   574779596      1359.08        5.7478E+12  989870553
   2723168908           6 Idle
 
Streams AQ: qmn slave idle wait                                       210760              0   574777271      2727.16        5.7478E+12 1830121438
   2723168908           6 Idle
 
latch free                                                              5281              2        8572         1.62          85723329 3474287957
   1893977003           0 Other
 
wait list latch free                                                       2              0           2         1.08             21602 2530878290
   1893977003           0 Other
 
inactive session                                                          10             10         978        97.75           9775371 3757863830
   1893977003           0 Other
 
latch: session allocation                                               2808              0        4372         1.56          43720071 2900750527
   1893977003           0 Other
 
enq: CI - contention                                                       6              0           3          .52             31329 1760863753
   1893977003           0 Other
 
latch: messages                                                           32              0           1          .03              8937 1973577887
   1893977003           0 Other
 
rdbms ipc reply                                                       116655              4       31156          .27         311562934 2587381521
   1893977003           0 Other
 
latch: enqueue hash chains                                                51              0           4          .08             41537 1847483002
   1893977003           0 Other
 
reliable message                                                        2801              4         566           .2           5663166  906644781
   1893977003           0 Other
 
SGA: allocation forcing component growth                                   8              7           9         1.09             87319 3493282803
   1893977003           0 Other
 
control file heartbeat                                                     1              1         391       390.68           3906807   40893507
   1893977003           0 Other
 
enq: CF - contention                                                    8036             20      138709        17.26        1387093730 1494394835
   1893977003           0 Other
 
enq: TC - contention                                                    3414              5        6927         2.03          69268342 1231322525
   1893977003           0 Other
 
latch: cache buffers lru chain                                          6695              0          47          .01            474300 3401628503
   1893977003           0 Other
 
latch: checkpoint queue latch                                             62              0           9          .15             94325   22066106
   1893977003           0 Other
 
latch: cache buffer handles                                                1              0           1          .99              9929 2935866945
   1893977003           0 Other
 
buffer deadlock                                                         2807           2788           3            0             26966  218992928
   1893977003           0 Other
 
latch: object queue header operation                                    3525              0          23          .01            229652  295718413
   1893977003           0 Other
 
LGWR wait for redo copy                                               118061              1         179            0           1793423 4266849434
   1893977003           0 Other
 
latch: redo allocation                                                  1543              0          72          .05            721412  266850936
   1893977003           0 Other
 
enq: FB - contention                                                       3              0           0          .02               457 1238611814
   1893977003           0 Other
 
latch: undo global data                                                  194              0          12          .06            115856 2221529869
   1893977003           0 Other
 
enq: TX - contention                                                      43              0         491        11.42           4912386 1629782133
   1893977003           0 Other
 
enq: US - contention                                                       1              0           0            0                20 2458904239
   1893977003           0 Other
 
instance state change                                                      3              1         142        47.25           1417641 1525267497
   1893977003           0 Other
 
wait for stopper event to be increased                                243311         106891     1441386         5.92        1.4414E+10 3065535233
   1893977003           0 Other
 
wait for a undo record                                                868239         174021     2705503         3.12        2.7055E+10 3020078888
   1893977003           0 Other
 
kksfbc child completion                                                   23             22         110         4.77           1097796    2679325
   1893977003           0 Other
 
cursor: pin S                                                              2              0           0            0                90  352301881
   1893977003           0 Other
 
PX qref latch                                                          59339          32464         127            0           1271750  175758063
   1893977003           0 Other
 
PX Deq Credit: send blkd                                              363427             38      135107          .37        1351067045 2610814049
   1893977003           0 Other
 
PX Deq: Signal ACK                                                       102              5          43          .42            427932  497835630
   1893977003           0 Other
 
enq: PS - contention                                                     183              0         558         3.05           5582783 2071012023
   1893977003           0 Other
 
latch: parallel query alloc buffer                                         9              0          13         1.39            125137  676951513
   1893977003           0 Other
 
PX Deq: Table Q qref                                                       5              0           0          .01               375 2049127157
   1893977003           0 Other
 
PX Deq: Table Q Get Keys                                                   4              1         407       101.65           4066117 4068211615
   1893977003           0 Other
 
Streams AQ: qmn coordinator waiting for slave to start                     2              0           1          .28              5620 1565566389
   1893977003           0 Other
 
enq: JS - queue lock                                                      32              0          10          .31             98585  306423829
   1893977003           0 Other
 
121 rows selected.

See Also

wait-events (ja)

Reference

http://docs.oracle.com/cd/B19306_01/server.102/b14237/waitevents.htm#REFRN101