DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE 手工清理awr

DBMS_WORKLOAD_REPOSITORY

The DBMS_WORKLOAD_REPOSITORY package lets you manage the Workload Repository, performing operations such as managing snapshots and baselines.



DROP_SNAPSHOT_RANGE Procedure

This procedure drops a range of snapshots.

Syntax

DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE(
   low_snap_id    IN  NUMBER,
   high_snap_id   IN  NUMBER
   dbid           IN  NUMBER DEFAULT NULL);

Parameters

Table 161-27 DROP_SNAPSHOT_RANGE Procedure Parameters

Parameter Description

low_snap_id

Low snapshot id of snapshots to drop.

high_snap_id

High snapshot id of snapshots to drop.

dbid

Database id (default to local DBID.


Examples

This example drops the range of snapshots between snapshot id 102 to 105 for the local database:

EXECUTE DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE(102, 105);

If you query the dba_hist_snapshot view after the Drop Snapshot action, you will see that snapshots 102 to 105 are removed from the Workload Repository.


MODIFY_SNAPSHOT_SETTINGS Procedures

This procedure controls three aspects of snapshot generation.

  • The INTERVAL setting affects how often snapshots are automatically captured.

  • The RETENTION setting affects how long snapshots are retained in the Workload Repository.

  • The number of SQL captured for each Top criteria. If the user manually specifies a value for Top N SQL, the AWR SQL collection will use the user-specified number for both automatic and manual snapshots.

There are two overloads. The first takes a NUMBER and the second takes a VARCHAR2 for the topnsql argument. The differences are described under the Parameters description.

Syntax

DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS(
   retention   IN  NUMBER    DEFAULT NULL,
   interval    IN  NUMBER    DEFAULT NULL,
   topnsql     IN  NUMBER    DEFAULT NULL,
   dbid        IN  NUMBER    DEFAULT NULL);

DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS(
   retention   IN  NUMBER    DEFAULT NULL,
   interval    IN  NUMBER    DEFAULT NULL,
   topnsql     IN  VARCHAR2,
   dbid        IN  NUMBER    DEFAULT NULL);

Parameters

Table 161-28 MODIFY_SNAPSHOT_SETTINGS Procedure Parameters

Parameter Description

retention

New retention time (in minutes). The specified value must be in the range of MIN_RETENTION (1 day) toMAX_RETENTION (100 years).

If ZERO is specified, snapshots will be retained forever. A large system-defined value will be used as the retention setting.

If NULL is specified, the old value for retention is preserved.

NOTE: The retention setting must be greater than or equal to the window size of the 'SYSTEM_MOVING_WINDOW' baseline. If the retention needs to be less than the window size, the MODIFY_BASELINE_WINDOW_SIZE Procedure can be used to adjust the window size.

interval

New interval setting between each snapshot, in units of minutes. The specified value must be in the rangeMIN_INTERVAL (10 minutes) to MAX_INTERVAL (1 year).

If ZERO is specified, automatic and manual snapshots will be disabled. A large system-defined value will be used as the retention setting.

If NULL is specified, the current value is preserved.

topnsql

  • If NUMBER: Top N SQL size. The number of Top SQL to flush for each SQL criteria (Elapsed Time, CPU Time, Parse Calls, Shareable Memory, Version Count). The value for this setting will not be affected by the statistics/flush level and will override the system default behavior for the AWR SQL collection. The setting will have a minimum value of 30 and a maximum value of 50,000. Specifying NULL will keep the current setting.

  • If VARCHAR2: Users are allowed to specify the following values: (DEFAULT, MAXIMUM, N), where N is the number of Top SQL to flush for each SQL criteria. Specifying DEFAULT will revert the system back to the default behavior of Top 30 for statistics level TYPICAL and Top 100 for statistics level ALL. Specifying MAXIMUM will cause the system to capture the complete set of SQL in the cursor cache. Specifying the number N is equivalent to setting the Top N SQL with the NUMBER type. Specifying NULLfor this argument will keep the current setting.

dbid

Database identifier in AWR for which to modify the snapshot settings. If NULL is specified, the local dbid will be used. Defaults to NULL.


Examples

This example changes the interval setting to one hour and the retention setting to two weeks for the local database:

EXECUTE DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS(
  interval  =>  60,
  retention =>  20160);

If you query the DBA_HIST_WR_CONTROL table after this procedure is executed, you will see the changes to these settings.

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