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About Advisors

Advisors arc powcrful tools for database managcment. Thcy providc spccific advicc on how to addrcss key managcment challcnges, covering a widc rangę of areas including space, performance, and undo managcment. In generał, advisors produce morę comprehcnsivc recommendations than alcrts. This is because alert generation is intended to be Iow cost and have minimal impact on performance, whcrcas advisors consume morę resourccs and perform morę detailed analysis. This, along with the what-if capability of some advisors, provides vital information for tuning that cannot be procured from any other source. Some advisors are run automatically.

Advisors are provided to help you improve database performance. These advisors include Automatic Database Diagnostic Monitor (ADDM). SQL advisors, and me mory

advisors. For example, the SGA Advisor graphically displays the impact on performance of changing the size of the System Global Area (SGA).

You can run a performance advisor when faced with the following situations:

■You want to resolve a problem in a specific area, for example, to determine why a given SQL statement is consuming 50 percent of CPU time and what to do to reduce its resource consumption.You can use the SQL Tuning Advisor.

■You are planning to add memory to your system. You can use the Memory Advisor to determine the database performance impact of increasing your SGA or PGA (Program Global Area).

You can also invokc some of the advisors from the Performance Hub page. or through recommendations from ADDM.