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4.15.3 Maintaining correct table indexing
The SQL Access Advisor, available from the Enterprise Manager, provides suggestions for
schema changes, including changes to indexes. You can find the SQL Access Advisor by
starting at the database home page, then following the Advisor Central link in the Related
Links section at the bottom of the page.
In our internal evaluation, we found that the following indexes are often helpful for BPMN
business processes. Consider these indexes as a starting point for defining indexes, and add
more indexes as described previously.
► create index PS.TASK_BIS on PS.LSW_TASK("BPD_INSTANCE_ID","STATUS");
► create index PDW.TASK_IDS on PDW.LSW_TASK("SYSTEM_ID","SYSTEM_TASK_ID");
► create index PS.TASK_UGI on PS.LSW_TASK("USER_ID","GROUP_ID","TASK_ID");
► create index PS.TASK_UI on PS.LSW_TASK("USER_ID","TASK_ID");
4.15.4 Sizing log files appropriately
Unlike DB2, Oracle performs an expensive checkpoint operation when switching logs. The
checkpoint involves writing all dirty pages in the buffer cache to disk. Therefore, an important
steps is to make the log files large enough that switching occurs infrequently. Applications that
generate a high volume of log traffic need larger log files to achieve this goal.
4.15.5 Using the Oracle SQL Tuning Advisor for long running SQL statements
If analysis shows that a particular SQL statement is taking a long time to execute, it might be
because the Oracle database is executing the SQL in a non-optimal manner. The Oracle SQL
Tuning Advisor can be used to optimize the performance of long running SQL statements.
Use the following methodology to identify, and improve, the performance of these SQL
statements:
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4.15.6 File system tuning
Identify long-running SQL statements by using an AWR report, or through the Event
Manager.
Run the SQL Tuning Advisor against the long-running SQL statements.
Evaluate and accept (as is appropriate) the recommendations from the SQL Tuning
Advisor.
For redo logs and control files on AIX, use a file system with agblksize parameter set to 512.
For other file systems, use the default agblksize.
4.15.7 Creating table spaces
When creating table spaces, consider minimizing the number of table space expansions
(extends) that occur by setting large initial and autoextend sizes. This step can help produce
fewer spikes in database utilization under peak load.
Alternatively, manually extend the table spaces during periods of relatively low activity to
mitigate this issue.
Chapter 4. Performance tuning and configuration 89