DBMS_SHARED_POOL: Pinning Objects

The DBMS_SHARED_POOL package provides procedures that allow PL/SQL objects and SQL cursors to be pinned (kept) in the Oracle shared pool. Once pinned, objects are not subject to the normal aging-out processes of the shared pool.

DBMS_SHARED_POOL is used primarily by DBAs to help solve memory management and performance issues that can arise when applications make use of large PL/SQL objects or SQL cursors. Two problems can arise when large objects need to be loaded into the shared pool:

  • ORA-04031 errors where insufficient memory is available and the user call fails to execute.

  • Degraded performance due to the memory management overhead involved in finding and making room to load large objects.

Pinning large objects into the shared pool when the Oracle instance is first started can reduce or eliminate these problems. Some DBAs use DBMS_SHARED_POOL in their database startup scripts to help ensure that shared pool memory is used efficiently.

Getting Started with DBMS_SHARED_POOL

The DBMS_SHARED_POOL package is created when the Oracle database is installed. The dbmspool.sql script (found in the built-in packages source code directory, as described in Chapter 1) contains the source code for this package’s specification. Unlike many of the other built-in package scripts, this script is not called by catproc.sql. Thus, the DBA must manually build this package. This is accomplished by executing the dbmspool.sql and prvtpool.plb scripts (in order) from SQLDBA ...

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