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Diagnosing Parallel Executions Performance

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April 15, 2010 5:00 AM

Billund, Denmark

Billund, Denmark

The purpose of parallel executions is to distribute the execution of a single SQL statement over several sessions executed by several CPUs. There are, naturally, advantages and disadvantages to this. The main advantage is related to performance. In fact, provided that necessary resources are available, response time might be dramatically reduced. The main disadvantage is that the diagnosis of performance problems is more difficult. This is mainly due to the fact that Oracle's instrumentation is mostly implemented at the session level. As a result, the challenge is to correctly aggregate information coming from several sessions in order to fully describe how a SQL statement is being executed. The aim of this presentation is to describe how to find, aggregate and interpret execution plans and statistics coming from V$ views such as active session history and SQL trace.

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