APPENDIX BOptimizer Parameters
There are lots of parameters that relate to optimization, and a number of them change their default value as you move from version to version. If you have a performance problem with a specific query after upgrading, it is always worth checking to see whether any of the parameters with new default values have names that seem be to related to the problem query.
For example, several people have complained about performance problems with executions plans that suddenly include the operation bitmap conversion(from rowids) after upgrading from 8i to 9i. Check the list of changes and you find that there is a parameter called _b_tree_bitmap_plans that has changed from false to true. Doesn't that sound like a good suspect? ...
Get Cost-Based Oracle Fundamentals now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
