Analyze Schema
Analyze Schema
-- use package (recommeded)
exec dbms_stats.gather_schema_stats(ownname => 'schema_name',options => 'GATHER STALE',estimate_percent => 5,method_opt => 'for all columns size auto',cascade=>true,degree=>20,stattab=>'T_name',statown=>'PERFSTAT',statid=>1);
 
-- analyze command (to be expired)
analyze table ... compute statistics for table for all indexes for all indexed columns;