Reference Note for Init.Ora Parameter “_FIX_CONTROL”.
- This parameter is a hidden (underscore) parameter
Such parameters should only ever be set under the guidance of Oracle Support. Clearly document why the parameter is set including reference to any SR, Bug or Note
Summary Version Information
Version Parameter Type Modifiable 11.1.0.6 _fix_control STRING
Allows Multiple ValuesALTER SESSION
ALTER SYSTEM (IMMEDIATE)10.2.0.4 _fix_control STRING
Allows Multiple ValuesALTER SESSION
ALTER SYSTEM (IMMEDIATE)10.2.0.3 _fix_control STRING
Allows Multiple ValuesALTER SESSION
ALTER SYSTEM (IMMEDIATE)
Support and Historical Notes for “_FIX_CONTROL”
_FIX_CONTROL is a special hidden parameter introduced in 10.2.0.2 which can be used to enable or disable certain bug fixes. This is typically used in the optimizer area to allow specific fixes to be turned on or off as some fixes can have a significant effect on execution plans. See details of any individual fix to know if the fix is enabled or disabled by default. Often the default setting (ON or OFF) for a fix is determined by the value of the OPTIMIZER_FEATURES_ENABLE parameter Note:62337.1 . The "Known Bugs" section below describes only some of the fixes which are under fix control. A full list of bug numbers which are controlled by fix control can be found in the V$ views: - V$SYSTEM_FIX_CONTROL - V$SESSION_FIX_CONTROL Other code areas besides the optimizer can use this parameter to control if a fix is on or off. The general format for this parameter is the form: _FIX_CONTROL='bug_number:ON|OFF' eg: alter session set "_fix_control"='4969880:ON'; or in the init.ora _fix_control='4969880:ON' Multiple values can be specified: eg: alter session set "_fix_control"='4969880:ON','5483301:off'; Note that fixes that use _FIX_CONTROL in one release may not use it in other releases so any settings should be reviewed when upgrading / downgrading or applying a patch set. Also some fix controls have numeric settings rather than ON or OFF.
NB Bug Fixed Description 8544722 10.2.0.5 Wrong Results with parallel and multiple Hash Joins 6006300 10.2.0.4 Push predicate does not occur 8560951 10.2.0.5, 11.2.0.2, 12.1.0.0 No view merging with scalar subquery in SELECT list with fix for bug 5395270 8685327 11.2.0.2, 12.1.0.0 An inefficient Index Full Scan may be used if index has “empty” stats 8864941 11.2.0.2, 12.1.0.0 Wrong results from join elimination with nested subqueries in the WHERE clause 9664387 11.2.0.2, 12.1.0.0 ORA-32036 on WITH queries with fix for bug 9468216 9380298 11.2.0.2, 12.1.0.0 Allow JPPD heuristics to produce cartesian product 9754681 11.2.0.2, 12.1.0.0 ORA-1424 SQL with LIKE and bind variable in multibyte 9861859 11.2.0.2, 12.1.0.0 OERI [kkmupsViewDestFro_4] from MERGE statement with join elimination 9882805 11.2.0.2, 12.1.0.0 Wrong results with NATIVE FULL OUTER JOIN and NVL 9468216 12.1.0.0 WITH subquery with constant FALSE predicate may be materialized giving poor plan 9088510 12.1.0.0 Predicate transformations not performed BEFORE query transformations 8800514 11.2.0.2, 12.1.0.0 Slow Parsing with subqueries 9011590 11.2.0.2, 12.1.0.0 Wrong results due to join elimination 8771297 11.2.0.2, 12.1.0.0 ORA-979 from GROUP BY with select list subquery 9826886 11.2.0.2, 12.1.0.0 Wrong results from query with outer join 9670261 11.2.0.2, 12.1.0.0 Wrong results with OUTER JOIN and subquery with filter 8781951 11.2.0.2, 12.1.0.0 Wrong results / error from MIN / MAX on partitioning column + 9495697 11.2.0.2, 12.1.0.0 Wrong results with OR predicates on same column 9691176 11.2.0.2, 12.1.0.0 OERI [kkeiis:1] querying hybrid partitioned table 8418388 11.2.0.2, 12.1.0.0 Wrong _FIX_CONTROL settings cause other parameters to be erased 9524564 11.2.0.2, 12.1.0.0 ORA-1424 parsing query using LIKE with binds and ESCAPE characters 9038070 10.2.0.5, 11.2.0.2 Wrong results with correlated subqueries using [NOT] LIKE predicates and fix for bug 7032684 9198871 10.2.0.5, 11.2.0.2 Dump on evaopn3 by query using ORDER BY and Function Based Index 9698413 11.2.0.2 Wrong Results for query with multiple filter predicates on one column (missing predicate) 9480478 11.2.0.2 Pushdown of bloom filter gives wrong results 8772028 11.2.0.2 OERI:qctcte1 parsing SQL with ORDER BY in a view 7450629 10.2.0.5, 11.2.0.1 Dump in QKSQBFIND1ROWTABS due to fix 5741044 7170213 10.2.0.5, 11.2.0.1 Put ORA-12842 from parallel query under _fix_control 7509689 10.2.0.5, 11.2.0.1 Cannot startup with bad value in “_fix_control” 7633439 11.2.0.1 Wrong results from join elimination 6438892 11.1.0.7, 11.2.0.1 Suboptimal plan with ROWNUM predicate and NESTED LOOPS 6972291 10.2.0.5, 11.2.0.1 Column group selectivity is not used when there is a histogram on one column 7420504 10.2.0.5, 11.2.0.1 Wrong Results with ANSI queries and fix for bug 7345484 7142215 10.2.0.5, 11.2.0.1 Wrong results for query using EXISTS and GROUP BY 8278320 10.2.0.5, 11.2.0.1 Wrong results from CONNECT BY with ORDER BY 7421721 11.2.0.1 Bad cardinality from CHAR col <op> :bind if OPTIMIZER_FEATURES_ENABLE <= 10.2.0.4 6440977 10.2.0.5, 11.2.0.1 Redundant predicates are not recognized across a join 6012093 10.2.0.5, 11.2.0.1 Suboptimal Execution Plan / Wrong Results / dump on qkaconAllocJoinKeys 6999937 11.2.0.1 Dump on evaopn3 with function based indexes 8447623 11.2.0.1 Wrong Results with OUTER joins and tables with Check Constraints 5099019 10.2.0.5, 11.2.0.1 DBMS_STATS does not count empty leaf_blocks 6626018 10.2.0.5, 11.1.0.7, 11.2.0.1 Cost of Subquery in a filter operation computed too low 6503543 10.2.0.5, 11.1.0.7, 11.2.0.1 Suboptimal plan due to bad cardinality estimate for RANGE join predicates 6708183 11.1.0.7, 11.2.0.1 CBO cannot get good cardinality estimate for TABLE() functions 6987082 10.2.0.5, 11.2.0.1 Overestimated Multicolumn Selectivity/ Join Predicate Not Pushed into UNION View 6797740 10.2.0.5, 11.1.0.7, 11.2.0.1 Dump [kkqvmValidAJView] using a SQL WITH clause and anti join 6430500 10.2.0.5, 11.2.0.1 CBO does not favour fully qualified unique index 7168184 11.2.0.1 Enhancement to allow multi-column bloom filter predicate pushdown 6326934 10.2.0.5, 11.1.0.7, 11.2.0.1 Poor selectivity for equality of fixed CHAR column with VARCHAR2 bind 6917874 10.2.0.4.1, 10.2.0.5, 11.1.0.7 Wrong results from multi level push of join predicates 5705630 10.2.0.4, 11.1.0.7 Suboptimal plan from ‘or’ expansion 6122097 10.2.0.5, 11.1.0.7 Wrong Results/Dump [evaopn2] with function based index present 8855781 11.1.0.7 Zero Cardinality estimation for Outer Join due to fix for Bug:4545802 5892599 11.2.0.1 Slow query performance with Hash Join on 1-row correlated subquery 5483301 10.2.0.4, 11.1.0.6 Cardinality of 1 when predicate value non-existent in frequency histogram 5714944 10.2.0.5, 11.1.0.6 CBO may choose INDEX SKIP SCAN instead of INDEX UNIQUE SCAN 5397482 10.2.0.4, 11.1.0.6 Wrong results from Star transformation with transitive join predicate 5015557 9.2.0.8, 10.2.0.3, 11.1.0.6 Dump under kkoNewExtractedBMKey or qerixGetKey with bitmap plan and function based index 4600710 10.2.0.3, 11.1.0.6 Improve costing for INLISTs in some cases 5040753 10.2.0.4, 11.1.0.6 Optimal index is not picked on simple query / Column group statistics 4422100 10.2.0.4, 11.1.0.6 Sort merge join on inequality should have control parameter 6050882 10.2.0.4, 11.1.0.6 Wrong results from ANSI outer join with fix for bug 4967068 or 5864217 + 4969880 9.2.0.8, 10.2.0.3, 11.1.0.6 Allow the fix for bug 3646162 to be disabled 5548510 10.2.0.4, 11.1.0.6 _FIX_CONTROL parameter leaks memory in the shared pool 7325597 10.2.0.5 Suboptimal plan if index only access available with fix for bug 6120483 8342682 10.2.0.5, 11.2.0.2 ORA-979 from GROUP BY with fix for bug 5520732 enabled
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