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 10.2.0.3. The list is up to 1070 items in 12.1.0.2.
Oracle Scratchpad 
[…] 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 […]
Pingback by Upgrades « Oracle Scratchpad — February 20, 2012 @ 5:53 pm GMT Feb 20,2012 |
[…] code has been back-ported to 10.2.0.4 (and 10.2.0.5) 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 […]
Pingback by Index Upgrades « Oracle Scratchpad — March 9, 2012 @ 6:06 pm GMT Mar 9,2012 |
[…] that’s reported as fixed in 12c, with a couple of patches for 11.2.0.2/3. However, setting “_fix_control”=’4887636:off’, does bypass the problem. (The fix control, introduced in 11.1.0.6 has […]
Pingback by first_rows(10) | Oracle Scratchpad — October 31, 2014 @ 5:32 pm GMT Oct 31,2014 |
[…] as they upgrade to a newer version of Oracle. The change occurred at 11.2.0.2 as revealed by fix control 9303766 which has the description: “use 1/NDV+1/NROWS for col1 LIKE col2 […]
Pingback by Cardinality Change | Oracle Scratchpad — December 8, 2014 @ 9:35 pm GMT Dec 8,2014 |
[…] a coding error in 11g that has been fixed in 12c – I couldn’t find an official bug or fix_control that matched, though. More on that later in the […]
Pingback by Upgrades – again | Oracle Scratchpad — October 28, 2018 @ 6:32 pm GMT Oct 28,2018 |
[…] There is some scope (with the usual “confirm with Oracle support” caveat) for modifying this behaviour with a fix_control: […]
Pingback by Hash Aggregation – 2 | Oracle Scratchpad — January 20, 2022 @ 12:45 pm GMT Jan 20,2022 |
[…] by default, and it’s not something you can tweak into a query with the opt_param() hint. Fix control 509019 has the description: “set leaf blocks to the number of blocks in the index extent […]
Pingback by Index FFS Cost 2 | Oracle Scratchpad — January 20, 2022 @ 12:48 pm GMT Jan 20,2022 |
[…] on 10.2.0.4, and that it wasn’t available in 9.2.0.8. There are two possibilities – a fix control, and an […]
Pingback by Index FFS Cost | Oracle Scratchpad — January 20, 2022 @ 12:48 pm GMT Jan 20,2022 |
[…] you want to adjust the granularity, see Franck Pachot’s note on parse time that describes bug/fix_control […]
Pingback by Most Recent – 2 | Oracle Scratchpad — January 20, 2022 @ 12:49 pm GMT Jan 20,2022 |
[…] system, session, or statement level – but there’s seems to be little point in using the fix_control approach (which might be a little obscure for the next developer to see the code) when it seems to […]
Pingback by Group by Elimination | Oracle Scratchpad — January 20, 2022 @ 12:50 pm GMT Jan 20,2022 |
[…] an example from my killer_parse.sql query after setting “_fix_control“=’16923858:4′ (1e4 microseconds = 1/100th second) in an instance of […]
Pingback by Parse Time | Oracle Scratchpad — January 20, 2022 @ 12:52 pm GMT Jan 20,2022 |
[…] iteration and index range scans and cardinality calculations – here’s a quick sample of v$system_fix_control in […]
Pingback by num_index_keys | Oracle Scratchpad — January 20, 2022 @ 12:53 pm GMT Jan 20,2022 |
[…] the hint didn’t seem to have any effect in that version of Oracle – even though the fix_control that seemed to be the most relevant (QKSFM_DBMS_STATS_24952618) was set to 1, so maybe the hint was […]
Pingback by system_stats() hint | Oracle Scratchpad — January 26, 2022 @ 9:46 am GMT Jan 26,2022 |