Selected articles, tweets, videos and photos from Tuesday’s events:Comments Off on Oracle OpenWorld 2012 – Latest News (Oct02) | Filed in Oracle | Tags: oow
Selected articles and tweets from Sunday and Monday’s events:Comments Off on Oracle OpenWorld 2012 – Latest News (Oct01) | Filed in Oracle | Tags: oow
Here is what happened today during the briefing:Comments Off on Oracle ACE Director Product Briefing 2012 – Day 2 | Filed in Oracle | Tags: aced, oow
Here is the story:Comments Off on Oracle ACE Director Product Briefing 2012 – Day 1 | Filed in Oracle | Tags: aced, oow
One of the world’s largest technology conferences is going to start shortly. Oracle OpenWorld 2012 will officially kick off this Sunday, September 30. I will be attending and hope to see you there.
Last year’s event hosted more than 45,000 registered attendees from 117 countries. With eight new acquisitions so far this year, I expect the 2012 event to be even bigger, more than 50,000 attendees and 2,000 sessions.Comments Off on How Big Will Oracle OpenWorld Be This Year? | Filed in Oracle | Tags: oow
Dating back to January 2001.Comments Off on Oracle Magazine Ask Tom Columns, the Whole List | Filed in Oracle | Tags: database
Dating back to January 2003.Comments Off on Oracle Magazine PL/SQL Columns by Steven Feuerstein, the Whole List | Filed in Oracle | Tags: pl/sql
Via Puneet Rajkumar.Comments Off on Handy Oracle EBS Trading Community Architecture (TCA) Diagram | Filed in Oracle | Tags: EBS
Christian Antognini published a handy list of currently available levels.Comments Off on Extended SQL Trace (Event 10046) Full List of Levels | Filed in Oracle | Tags: debugging
If you are on 10g, or if on 11g but ACS (Adaptive Cursor Sharing) is not an option, then deleting column Histograms may be your best option to improve your plan stability. Like any other change, you rather test first on a non-production environment. Even in such test environment, you may want to restrict your test to only those tables accessed by your SQL. On 11g, DBMS_STATS.DELETE_COLUMN_STATS provides an option to delete just the Histograms while preserving all other column statistics. This is by using parameter COL_STAT_TYPE with value HISTOGRAM. If you want to do the same on 10g, you may want to use the SQLT HGRM module. In any case you can always restore column statistics using DBMS_STATS.RESTORE_TABLE_STATS.
Carlos gives us a tip on how to disable the use of Histograms with a hidden parameter:
If you are considering deleting Histograms to test the effect on an execution plan and the performance of your SQL, you may want to test first asking the CBO to simply ignore them. If patch for bug 9550277 has been applied in your system then you can command below.
ALTER SESSION SET “_FIX_CONTROL”=’9550277:1′;
Worth noting that Jonathan Lewis was very successful in tuning a customer’s query by simply deleting histograms:
The most critical piece of advice I had given them was to get rid of ALL the histograms they had on their system, and then watch very carefully for any signs that they might need to re-introduce a handful of histograms over the next few weeks. One of their critical queries completed in less that 2 seconds when histograms were removed, but took 33 seconds to complete when histograms were in place.Comments Off on Delete Column Histograms to Improve SQL Plan Stability | Filed in Oracle | Tags: performance