134 DBMS_RESULT_CACHE

The DBMS_RESULT_CACHE package provides an interface to allow the DBA to administer that part of the shared pool that is used by the SQL result cache and the PL/SQL function result cache.

Both these caches use the same infrastructure. Therefore, for example, DBMS_RESULT_CACHE.BYPASS determines whether both caches are bypassed or both caches are used, and DBMS_RESULT_CACHE.FLUSH flushes both all the cached results for SQL queries and all the cached results for PL/SQL functions.

This chapter contains the following topics:

See Also:

134.1 DBMS_RESULT_CACHE Security Model

Only database administrators should be granted the EXECUTE privilege for this package.

134.2 DBMS_RESULT_CACHE Constants

The DBMS_RESULT_CACHE package defines several constants for specifying parameter values.

The following table describes these constants.

Table 134-1 DBMS_RESULT_CACHE Constants

Constant Definition

STATUS_BYPS

CONSTANT VARCHAR(10) := 'BYPASS';

STATUS_CORR

CONSTANT VARCHAR(10) := 'CORRUPT';

STATUS_DISA

CONSTANT VARCHAR(10) := 'DISABLED';

STATUS_ENAB

CONSTANT VARCHAR(10) := 'ENABLED';

STATUS_SYNC

CONSTANT VARCHAR(10) := 'SYNC';

134.3 Summary of DBMS_RESULT_CACHE Subprograms

This table lists the DBMS_RESULT_CACHE subprograms and briefly describes them.

Table 134-2 DBMS_RESULT_CACHE Package Subprograms

Subprogram Description

BLACK_LIST Function

Returns a pipelined BL_TABT.

BLACK_LIST_ADD Procedure

Adds a cache_id to the black-list.

BLACK_LIST_CLEAR Procedure

Removes all cache_ids from the black-list.

BLACK_LIST_REMOVE Procedure

Removes the cache_id from the black-list.

BYPASS Procedure

Sets the bypass mode for the Result Cache

FLUSH Function & Procedure

Attempts to remove all the objects from the Result Cache, and depending on the arguments retains or releases the memory and retains or clears the statistics

INVALIDATE Functions & Procedures

Invalidates all the result-set objects that dependent upon the specified dependency object

INVALIDATE_OBJECT Functions & Procedures

Invalidates the specified result-set object(s)

MEMORY_REPORT Procedure

Produces the memory usage report for the Result Cache

STATUS Function

Checks the status of the Result Cache

134.3.1 BLACK_LIST Function

This function returns all the blacklisted cache ids of a local instance.

Syntax

DBMS_RESULT_CACHE.BLACK_LIST
   RETURN BL_TABT;

134.3.2 BLACK_LIST_ADD Procedure

This procedure adds a cache_id to the black-list.

Syntax

DBMS_RESULT_CACHE.BLACK_LIST_ADD (
   cache_id   IN  VARCHAR2,
   global     IN  BOOLEAN DEFAULT FALSE);

Parameters

Table 134-3 BLACK_LIST_ADD Procedure Parameters

Parameter Description

cache_id

The cache_id is added to the black-list.

global

TRUE — applies to all caches in a RAC cluster.

FALSE (default) — applies only to the local instance cache.

134.3.3 BLACK_LIST_CLEAR Procedure

This procedure removes all cache_ids from the black-list.

Syntax

DBMS_RESULT_CACHE.BLACK_LIST_CLEAR (
   global   IN  BOOLEAN DEFAULT FALSE);

Parameters

Table 134-4 BLACK_LIST_CLEAR Procedure Parameters

Parameter Description

global

TRUE — applies to all caches in a RAC cluster.

FALSE (default) — applies only to the local instance cache.

134.3.4 BLACK_LIST_REMOVE Procedure

This procedures removes the cache_id from the black-list.

Syntax

DBMS_RESULT_CACHE.BLACK_LIST_REMOVE (
   cache_id   IN  VARCHAR2,
   global     IN  BOOLEAN DEFAULT FALSE); 

Parameters

Table 134-5 BLACK_LIST_REMOVE Procedure Parameters

Parameter Description

cache_id

The cache_id is removed from the black-list.

global

TRUE — applies to all caches in a RAC cluster.

FALSE (default) — applies only to the local instance cache.

134.3.5 BYPASS Procedure

This procedure sets the bypass mode for the Result Cache.

It sets one of the following bypass modes:

  • When bypass mode is turned on, it implies that cached results are no longer used and that no new results are saved in the cache.

  • When bypass mode is turned off, the cache resumes normal operation.

Syntax

DBMS_RESULT_CACHE.BYPASS (
   bypass_mode    IN   BOOLEAN,
   session        IN   BOOLEAN);

Parameters

Table 134-6 BYPASS Procedure Parameters

Parameter Description

bypass_mode

  • TRUE => Result Cache usage is bypassed

  • FALSE => Result Cache usage is turned on

session

  • TRUE => Applies to current session

  • FALSE (default) => Applies to all sessions

Usage Notes

This operation is database instance specific.

Examples

This operation can be used when there is a need to hot patch PL/SQL code in a running system. If a code-patch is applied to a PL/SQL module on which a result cached function directly or transitively depends, then the cached results associated with the result cache function are not automatically flushed (if the instance is not restarted/bounced). This must be manually achieved.

To ensure correctness during the patching process follow these steps:

  1. Place the result cache in bypass mode, and flush existing result.

    BEGIN
       DBMS_RESULT_CACHE.BYPASS(TRUE);
       DBMS_RESULT_CACHE.FLUSH;
    END;
    /
    

    This step must be performed on each instance if in a Oracle Real Application Clusters environment.

  2. Apply the PL/SQL code patches.

  3. Resume use of the result cache, by turning off the cache bypass mode.

    BEGIN
       DBMS_RESULT_CACHE.BYPASS(FALSE);
    END;
    /
    

    This step must be performed on each instance if in a Oracle Real Application Clusters environment.

134.3.6 FLUSH Function & Procedure

This function and procedure attempts to remove all the objects from the Result Cache, and depending on the arguments retains or releases the memory and retains or clears the statistics.

Syntax

DBMS_RESULT_CACHE.FLUSH (
   retainMem  IN  BOOLEAN DEFAULT FALSE,
   retainSta  IN  BOOLEAN DEFAULT FALSE) 
  RETURN BOOLEAN;
DBMS_RESULT_CACHE.FLUSH (
   retainMem  IN  BOOLEAN DEFAULT FALSE,
   retainSta  IN  BOOLEAN DEFAULT FALSE); 

Parameters

Table 134-7 FLUSH Function & Procedure Parameters

Parameter Description

retainMem

  • TRUE => retains the free memory in the cache

  • FALSE (default) => releases the free memory to the system

retainSta

  • TRUE => retains the existing cache statistics

  • FALSE (default) => clears the existing cache statistics

Return Values

TRUE if successful in removing all the objects.

134.3.7 INVALIDATE Functions & Procedures

This function and procedure invalidates all the result-set objects that dependent upon the specified dependency object.

Syntax

DBMS_RESULT_CACHE.INVALIDATE (
   owner        IN  VARCHAR2, 
   name         IN  VARCHAR2) 
 RETURN NUMBER;
DBMS_RESULT_CACHE.INVALIDATE (
   owner       IN  VARCHAR2, 
   name        IN  VARCHAR2);
DBMS_RESULT_CACHE.INVALIDATE (
  object_id    IN BINARY_INTEGER) 
 RETURN NUMBER;
DBMS_RESULT_CACHE.INVALIDATE (
   object_id    IN BINARY_INTEGER);

Parameters

Table 134-8 INVALIDATE Function & Procedure Parameters

Parameter Description

owner

Schema name

name

Object name

object_id

Dictionary object number

Return Values

The number of objects invalidated.

134.3.8 INVALIDATE_OBJECT Functions & Procedures

This function and procedure invalidates the specified result-set object(s).

Syntax

DBMS_RESULT_CACHE.INVALIDATE_OBJECT (
   id          IN  BINARY_INTEGER) 
 RETURN NUMBER;
DBMS_RESULT_CACHE.INVALIDATE_OBJECT (
   id          IN  BINARY_INTEGER);
DBMS_RESULT_CACHE.INVALIDATE_OBJECT (
  cache_id     IN  VARCHAR2) 
 RETURN NUMBER;
DBMS_RESULT_CACHE.INVALIDATE_OBJECT (
   cache_id   IN  VARCHAR2);

Parameters

Table 134-9 INVALIDATE_OBJECT Function & Procedure Parameters

Parameter Description

id

Address of the cache object in the Result Cache

cache_id

Cache-id

Return Values

The number of objects invalidated.

134.3.9 MEMORY_REPORT Procedure

This procedure produces the memory usage report for the Result Cache.

Syntax

DBMS_RESULT_CACHE.MEMORY_REPORT (
   detailed   IN   BOOLEAN DEFAULT FALSE);

Parameters

Table 134-10 MEMORY_REPORT Procedure Parameters

Parameter Description

detailed

  • TRUE => produces a more detailed report

  • FALSE (default) => produces the standard report

Usage Notes

Invoking this procedure from SQL*Plus requires that the serveroutput be turned on.

134.3.10 STATUS Function

This function checks the status of the Result Cache.

Syntax

DBMS_RESULT_CACHE.STATUS
   RETURN VARCHAR2;

Return Values

One of the following values:

  • STATUS_DISA - Cache is not available

  • STATUS_ENAB - Cache is available

  • STATUS_BYPS: Cache has been made temporarilyunavailable.

  • STATUS_SYNC - Cache is available, but synchronizing with Oracle RAC nodes