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.

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.

Oracle database features wish list – 1

Sometimes it just happens when you want some functionality built into Oracle database. I think I’ll put on the blog my “wish list” items to not forget about them. Today’s one: I want to have an option to reduce bind variables dumping in the SQL trace based on SQL depth level. For instance, to dump only those variables which were used in top level calls only. It could be useful in case of queries with PL/SQL function calls with SQL in it, producing enormous amount of info in the trace file which you probably don’t want to see because you are interested in the “driving” bind variables only. Or in case of globally enabled tracing – again it’s possible that you probably don’t need bind variables from all executed statements and/or want to reduce generated trace files total size.

SQL_TRACE is deprecated, really

Just a quick note that SQL_TRACE parameter is no longer valid – it is deprecated as of Oracle 10g Release 2 in favor of DBMS_MONITOR subprograms. I realized that after start up warning:

SQL> startup
ORA-32004: obsolete or deprecated parameter(s) specified for RDBMS instance
ORACLE instance started.

Though SQL_TRACE is still working in 11.2.0.1, it’s a good idea to start forgetting about it.