113 DBMS_OUTLN
The DBMS_OUTLN package, synonymous with OUTLN_PKG, contains the functional interface for subprograms associated with the management of stored outlines.
See Also:
For more information about using the DBMS_OUTLN package, see Oracle Database SQL Tuning Guide.
Note:
Stored outlines will be desupported in a future release in favor of SQL plan management. In Oracle Database 11g Release 1 (11.1), stored outlines continue to function as in past releases. However, Oracle strongly recommends that you use SQL plan management for new applications. SQL plan management creates SQL plan baselines, which offer superior SQL performance and stability compared with stored outlines.If you have existing stored outlines, please consider migrating them to SQL plan baselines by using the LOAD_PLANS_FROM_CURSOR_CACHE Functions or LOAD_PLANS_FROM_SQLSET Function of the DBMS_SPM package. When the migration is complete, you should disable or remove the stored outlines.
This chapter contains the following topics:
113.1 DBMS_OUTLN Overview
A stored outline is the stored data that pertains to an execution plan for a given SQL statement. It enables the optimizer to repeatedly re-create execution plans that are equivalent to the plan originally generated along with the outline.The data stored in an outline consists, in part, of a set of hints that are used to achieve plan stability.
Stored outlines will be de-supported in a future release in favor of SQL plan management. As of 11g R1, stored outlines continue to function as in past releases, but Oracle strongly recommends that you use SQL plan management for new applications. SQL plan management creates SQL plan baselines, which offer superior SQL performance and stability compared with stored outlines.If you have existing stored outlines, please consider migrating them to SQL plan baselines by using the LOAD_PLANS_FROM_CURSOR_CACHE Functions or the LOAD_PLANS_FROM_SQLSET Function of the DBMS_SPM package. When the migration is complete, you should disable or remove the stored outlines.
113.2 DBMS_OUTLN Security Model
DBMS_OUTLN contains management procedures that should be available to appropriate users only. EXECUTE privilege is not extended to the general user community unless the DBA explicitly does so.
PL/SQL functions that are available for outline management purposes can be executed only by users with EXECUTE privilege on the procedure (or package).
113.3 Summary of DBMS_OUTLN Subprograms
This table lists the DBMS_OUTLN subprograms and briefly describes them.
Table 113-1 DBMS_OUTLN Package Subprograms
| Subprogram | Description |
|---|---|
|
Clears the outline 'used' flag |
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|
Generates outlines from the shared cursor identified by hash value and child number |
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|
Drops outlines that belong to a specified category |
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|
Drops outlines that have never been applied in the compilation of a SQL statement |
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Updates outline signatures to those that compute based on exact text matching |
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|
Changes the category of outlines in one category to a new category |
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|
Updates outline signatures to the current version's signature |
113.3.1 CLEAR_USED Procedure
This procedure clears the outline 'used' flag.
Syntax
DBMS_OUTLN.CLEAR_USED ( name IN VARCHAR2);
Parameters
Table 113-2 CLEAR_USED Procedure Parameters
| Parameter | Description |
|---|---|
|
|
Name of the outline. |
113.3.2 CREATE_OUTLINE Procedure
This procedure generates an outline by reparsing the SQL statement from the shared cursor identified by hash value and child number.
Syntax
DBMS_OUTLN.CREATE_OUTLINE ( hash_value IN NUMBER, child_number IN NUMBER, category IN VARCHAR2 DEFAULT 'DEFAULT');
Parameters
Table 113-3 CREATE_OUTLINE Procedure Parameters
| Parameter | Description |
|---|---|
|
|
Hash value identifying the target shared cursor. |
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Child number of the target shared cursor. |
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|
Category in which to create outline (optional). |
113.3.3 DROP_BY_CAT Procedure
This procedure drops outlines that belong to a particular category. While outlines are put into the DEFAULT category unless otherwise specified, users have the option of grouping their outlines into groups called categories.
Syntax
DBMS_OUTLN.DROP_BY_CAT ( cat VARCHAR2);
Parameters
Table 113-4 DROP_BY_CAT Procedure Parameters
| Parameter | Description |
|---|---|
|
|
Category of outlines to drop. |
Usage Notes
This procedure purges a category of outlines in a single call.
Examples
This example drops all outlines in the DEFAULT category:
DBMS_OUTLN.DROP_BY_CAT('DEFAULT'); 113.3.4 DROP_UNUSED Procedure
This procedure drops outlines that have never been applied in the compilation of a SQL statement.
Syntax
DBMS_OUTLN.DROP_UNUSED;
Usage Notes
You can use DROP_UNUSED for outlines generated by an application for one-time use SQL statements created as a result of dynamic SQL. These outlines are never used and take up valuable disk space.
113.3.5 EXACT_TEXT_SIGNATURES Procedure
This procedure updates outline signatures to those that compute based on exact text matching.
Syntax
DBMS_OUTLN.EXACT_TEXT_SIGNATURES;
Usage Notes
This procedure is relevant only for downgrading an outline to 8.1.6 or earlier.
113.3.6 UPDATE_BY_CAT Procedure
This procedure changes the category of all outlines in one category to a new category.
Syntax
DBMS_OUTLN.UPDATE_BY_CAT ( oldcat VARCHAR2 default 'DEFAULT', newcat VARCHAR2 default 'DEFAULT');
Parameters
Table 113-5 UPDATE_BY_CAT Procedure Parameters
| Parameter | Description |
|---|---|
|
|
The current category of outlines. |
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The new category of outlines. |
113.3.7 UPDATE_SIGNATURES Procedure
This procedure updates outline signatures to the current version's signature.
Syntax
DBMS_OUTLN.UPDATE_SIGNATURES;
Usage Notes
You should execute this procedure if you have imported outlines generated in an earlier release to ensure that the signatures are compatible with the current release's computation algorithm.