Statspack is a set of SQL, PL/SQL and SQL*Plus scripts which allow the collection, automation, storage and viewing of performance data. A user, PERFSTAT, is automatically created by the installation; owns all objects needed by this package. This user is granted limited query-only privileges on the V$views required for performance tuning. A Statspack report is generated from two snapshots, which is nothing but a collection of contents from various dynamic performance tables.
The DBMS_PROFILER package provides an interface to profile existing PL/SQL applications and identify performance bottlenecks. You can then collect and persistently store the PL/SQL profiler data.
DBMS_XPLAN.DISPLAY_CURSOR does not display execution plan of all children associated with the SQL_ID
Jun 152009
Per Oracle documentation, to display the execution plan of all children associated with the SQL ID; you would have to call the table function in below format.
You can have multiple instances on the same machine, each with their own data files, either sharing the ORACLE_HOME or each with different ORACLE_HOME. ORACLE_HOME and ORACLE_SID are the key environment variables used by Oracle to identify an instance. In addition $ORACLE_HOME/bin must be in your PATH environment variable. To check the value of these [...]
To execute any SQL statement Oracle has to derive an ‘execution plan’ . The execution plan of a query is a description of how Oracle will implement the retrieval of data to satisfy a given SQL statement. It is nothing but a tree which contains the order of steps and relationship between them.
You can automatically get a report on the execution path used by the SQL optimizer and the statement execution statistics. The report is generated after successful SQL DML (that is, SELECT, DELETE, UPDATE and INSERT) statements. It is useful for monitoring and tuning the performance of these statements. To use this feature, you must create a PLAN_TABLE table in your schema and then have the PLUSTRACE role granted to you. DBA privileges are required to grant the PLUSTRACE role.
Methods required to obtain a formatted explain plan differ depending on which version of Oracle you are using. The initial steps to create a plan table and make the optimizer populate the plan table with the execution plan are common to all versions of Oracle.