Blogs

Mohamed.Houri
Follow /13 Jun 2017 at 3:33pm / Oracle Blog

Why my execution plan has not been shared - Part V

In this fifth installment of this series of articles about the non-sharing reasons that prevent Oracle from using an existing execution plan, we are going to dig into two new supplementary reasons: language_mismatch and auto_check_mismatch . The same...
542 0 /
Mohamed.Houri
Follow /5 May 2017 at 6:38pm / Oracle Blog

Why my execution plan has not been shared - Part IV

As mentioned in the previous three articles of the series there are sixty-four reasons for which the Oracle Optimizer might decide to hard parse a new execution plan instead of sharing the existing one. Out of these sixty-four reasons, we have already...
1030 0 /
Mohamed.Houri
Follow /26 Sep 2016 at 3:16pm / Oracle Blog

Why my execution plan has not been shared – Part III

In the previous instalment of this series we looked at four reasons from gv$sql_shared_cursor view and explained the situations and criteria for which Oracle is forced to compile a new execution plan. We used reproducible examples to demonstrate these...
1099 0 /
Mohamed.Houri
Follow /28 Jun 2016 at 1:08pm / Oracle Blog

Why my execution plan has not been shared – Part II

In an earlier article we discussed two very popular reasons, L OAD_OPTIMIZER_STATS and HASH_MATCH_FAILED pushing Oracle to refuse sharing an existing execution plan and, thereby, hard parsing a new plan. While the first reason is closely related to the...
1280 0 /
Mohamed.Houri
Follow /30 Apr 2016 at 7:26am / Oracle Blog

Why my execution plan has not been shared – Part I

For most people troubleshooting SQL query performance problems is a necessity rather than a preference. Very often they are using a trial and error strategy to overcome those frustrating situations. Unfortunately the trial and error method is not reliable...
2297 0 /
Mohamed.Houri
Follow /4 Sep 2014 at 11:17pm / Oracle Blog

12c Oracle Adaptive Join

Introduction I was thinking about the execution plan a 12c CBO ancestor would have come up with when the new 12c CBO produces an adaptive plan? This is why I've decided to engineer a simple use case and came up with few observations this article...
4024 0 /