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sql_trace

Adaptive STAT lines in SQL trace

Lately I’ve been using SQL runtime execution statistics combined with SQL monitor for performance diagnostics and, honestly, almost forgot about SQL trace. So this note is not very useful to me but it might be to someone: along with ALL_EXECUTIONS option appeared in (I believe) 11gR2, there’s a new option starting with 11.2.0.2 which can significantly decrease amount of data in the trace files for STAT lines compared to ALL_EXECUTIONS, still providing some of them from time to time.

Here is a case to demonstrate:

How to kill performance with 16MB table

If you think 16MB tables are so small that can’t be root cause of significant performance problems with SELECT queries, then read about my today’s headache – a story of 16MB table worth something like 270 seconds of response time. It began mostly as usual: an application web page didn’t show up within 5 minutes. [...]