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Performance Tuning Introduction
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一、Oracle Database 11g Enterprise Eidition
二、Oracle Database Enterprise Manager
三、Oracle Database Diagnostics Pack
1.Automatic Workload Repository
2.Automatic Database Diagnostic Monitor
3.Active Session History
四、Oracle Database Tuning Pack
1.SQL Tuning Advisor
2.SQL Access Advisor
五、Oracle Real Application Testing
1.Database Replay
2.SQL Performance Analyzer

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Performance Method
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一、Introduction
1.Performance Reason：
1)throughput
2)response time

2.Performance steps
1)get feedback from the system user and the people paying for the system
2)set performance goals

二、Gathering Database Statistics Using the Automatic Workload Repository
1.cumulative statistic

2.AWR Automatic Workload Repository (AWR)
1)automates database statistics gathering by collecting, processing, and maintaining performance statistics for database problem
2)detection
3)self-tuning purposes.

3.AWR snapshot

4.initialization parameters
1)statistics_level:TYPICAL and ALL(enable),BASIC(disable)
2)CONTROL_MANAGEMENT_PACK_ACCESS
DIAGNOSTIC+TUNING (default) or DIAGNOSTIC to enable automatic database diagnostic monitoring.
Setting CONTROL_MANAGEMENT_PACK_ACCESS to NONE disables many database features, including ADDM, and is strongly discouraged.

5.The database statistics collected and processed by AWR include:

1)Time Model Statistics
①DB Time：Database time is calculated by aggregating the CPU time and wait time of all active sessions
②DB Time：only time spent on client processes rather than background process，such as PMON
③goal： database tuning is to reduce database time

2)Wait Event Statistics
①latch,buffer,I/O contention

3)Session and System Statistics

4)Active Session History Statistics:
is samples of session activity in the database,
and stores them in a circular buffer in the System Global Area (SGA)

5)High-Load SQL Statistics

三、Using the Oracle Performance Method
1.Preparing the Database for Tuning
2.Proactive tuning:ADDM、real-time performance、alters。
3.Reactvie tuning
4.Tuning SQL Statements

四、Common Performance Problems Found in Oracle Databases

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