Oracle Database 11 g - Online Public Access Catalog

CHAPTER 4 ■ PERFORMANCE MANAGEMENT 217Here’s an example that shows how to create an ADDM directive to filter out findingsrelating to undersized instance memory:SQL> var task_name varchar2(100);SQL> begindbms_addm.insert_finding_direcive (null,'Undersized Instance Memory Directive','Undersize instance memory',5,10);:task_name := 'ADDM Task 1';dbms_addm_analyze_inst(:task_name,1,2);end;SQL> /The example shown here creates an instance ADDM task with a finding directive that limitsthe display of the “Undersized instance memory” finding only if that finding is related to atleast five active sessions during the time of the ADDM analysis. In addition, the finding mustbe responsible for at least 10 percent of the database time during the analysis period. You candelete any directive you create with the DELETE_* procedures. For example, the delete_finding_directive procedure will delete a finding directive.AWR BaselinesThe AWR generates automatic snapshots of performance data on an hourly basis. You can alsomanually generate snapshots with the DBMS_WORKLOAD_REPOSITORY package. The ADDM thenuses the data thus collected in the AWR.In Oracle Database 10g, you learned how to use AWR baselines, which provide a frame ofreference for comparing performance and advisor reports between two periods. An AWR baselineis simply database performance data from a set of AWR snapshots, representing databaseperformance at an optimum level. When a performance problem occurs, the database comparesperformance data from a previous “good” period with the performance of a similar workload.You create a baseline with the create_baseline procedure of the DBMS_WORKLOAD_REPOSITORYpackage and drop it by executing the drop_baseline procedure.■Note In Oracle Database 11g, the default retention for the snapshot data is eight days to ensure that theAWR always has a full week’s worth of performance data.You could create and delete only simple fixed baselines in Oracle Database 10g. A fixedbaseline uses a fixed period that you specify. Oracle Database 11g adds more sophisticationto the management of AWR baselines by providing the capability to create more complex andproductive baselines. Oracle Database 11g contains the following enhancements relating toAWR baselines: