ba6.us - Dave's Database Related Stuff

When working on a SQL Tuning issue I often kick off a SQL Tuning Advisor job on the SQL while I gather info about statistics and other things I like to check when tuning. After I get an idea of where performance might be suffering I use the SQL Tuning Advisor results for a second opion. Unfortunately more often than not the SQL Tuning Advisor reports it can dramatically improve the performance of a SQL Statement by using a SQL Profile to force a different plan.

I recently got this error while trying to run a SQL Tuning Task against a SQL statement that was available in AWR but not currently in the library cache.

I got around it by locating the SQL in OEM and using SQL Worksheet to execute it: Read more »

I recently had an issue where a query being submitted to the database had a large change in performance. I could attribute the change to a recent change in object statistics, but the query wasn't behaving because of a combination of a view, subquery, UNION, and LIKE operators. After spending too much time on this statement I decided to hint it to make it perform like it did before the most recent stats change.

Iggy Fernandez covers the topic of who is better suited to tune SQL - Developers or DBAs. Also listed are 5 Dangerous Beliefs which may influence the answer to that question.

http://iggyfernandez.wordpress.com/2009/07/12/who-should-tune-sql-the-dba-or-the-developer/

-Dave