Oracle Scratchpad

January 28, 2011

Fix Control

Filed under: Troubleshooting — Jonathan Lewis @ 3:35 pm BST Jan 28,2011

There’s a very useful posting from Coskan Gundogar about tracking down a problem to do with an 11g upgrade.

The method basically revolves around a quick check for “known issues” that might be relevant by looking at the dynamic performance views v$system_fix_control.

When I read Coskan’s notes I had forgotten that I had written a short item about this myself about a year ago where I listed the relatively small number of items available in The list is up to 1070 items in



  1. […] and fixes to the optimizer that take place I decided to take a look at recent developments in the “fix control” list, and the “optimizer environment” parameters. Here’s a breakdown of the […]

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  2. […] code has been back-ported to (and but requires you to set a value for the hidden _fix_control parameter (which you can do at the session or system level) to enable the feature. There are three […]

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  3. […] that’s reported as fixed in 12c, with a couple of patches for However, setting “_fix_control”=’4887636:off’, does bypass the problem. (The fix control, introduced in has […]

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  4. […] as they upgrade to a newer version of Oracle. The change occurred at as revealed by fix control 9303766 which has the description: “use 1/NDV+1/NROWS for col1 LIKE col2 […]

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