SQL Tuning Features

AWR and ADDM provide services to support automatic SQL tuning. SQL Tuning Advisor and SQL Access Advisor are the SQL tuning tools provided by Oracle.

Automatic Workload Repository

AWR provides services to Oracle Database 10g to collect, maintain, and utilize the statistics for problem detection and self-tuning. The AWR has an in-memory statistics collection facility, which is useful for 10g components to collect statistics. These metrics are stored in memory for performance reasons.

The memory version of the statistics is written to disk regularly by a new background process called MMON (Memory Monitor).

Oracle Database 10g captures and retains this historical data without DBA intervention. The default retention period is seven days using a retention parameter setting of 10080 which was as described in Chapter 4. The historic data is used for analysis of performance problems that occurred in a certain time period in the past and to do trend analysis.

As a review, some session and system statistics that are retained in v$sessstat and v$sysstat are as follows: