OCP 1Z0 053 71

71.The Automatic Database Diagnostic Monitor (ADDM) analysis runs every 60 minutes on your 
database. Your database is facing a series of interrelated problems over a period of two hours. You need 
to ensure that the ADDM analysis is run over a time span of two hours in future. What would you do? 
A. Create two custom ADDM tasks. 
B. Modify the AWR snapshot time interval to two hours. 
C. Create a new scheduler window for a time period of two hours. 
D. Modify the Automatic Workload Repository (AWR) snapshot retention period to two hours. 
Answer: B 

默认分析一个小时的信息，如果想分析两个时的，改下间隔时间。

SQL> SELECT * FROM DBA_HIST_WR_CONTROL;      DBID SNAP_INTERVAL                           RETENTION                               TOPNSQL---------- --------------------------------------- --------------------------------------- ----------1377411632 +00000 01:00:00.0                       +00008 00:00:00.0                       DEFAULT1 row selected

http://docs.oracle.com/cd/E11882_01/server.112/e41573/autostat.htm#PFGRF94187

5.3.1.3 Modifying Snapshot Settings

You can adjust the interval, retention, and captured Top SQL of snapshot generation for a specified database ID, but note that this can affect the precision of the Oracle Database diagnostic tools.

The INTERVAL setting affects how often the database automatically generates snapshots. The RETENTION setting affects how long the database stores snapshots in the workload repository. The TOPNSQL setting affects the number of Top SQL to flush for each SQL criteria (Elapsed Time, CPU Time, Parse Calls, sharable Memory, and Version Count). The value for this setting is not affected by the statistics/flush level and will override the system default behavior for the AWR SQL collection. It is possible to set the value for this setting to MAXIMUM to capture the complete set of SQL in the shared SQL area, though by doing so (or by setting the value to a very high number) may lead to possible space and performance issues because there will more data to collect and store. To adjust the settings, use the MODIFY_SNAPSHOT_SETTINGS procedure. For example:

BEGIN  DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS( retention => 43200,                  interval => 30, topnsql => 100, dbid => 3310949047);END;/

In this example, the retention period is specified as 43200 minutes (30 days), the interval between each snapshot is specified as 30 minutes, and the number of Top SQL to flush for each SQL criteria as 100. If NULL is specified, the existing value is preserved. The optional database identifier is 3310949047. If you do not specify a value for dbid, the local database identifier is used as the default value. You can check the current settings for your database instance with theDBA_HIST_WR_CONTROL view.