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Don Burleson Blog 







Oracle _cursor_features_enabled tips

Oracle Database Tips by Donald BurlesonApril 30,  2015

From OTN, the hidden parameter _cursor_features_enabled is used to correct an optimizer bug, the kksfbc child completion wait.  

A previous solution to excessive waits for the kksfbc child completion event was setting  _kks_use_mutex_pin=false to control the mutex, but Oracle also recommends setting _cursor_features_enabled = 10.

This hidden parameter should only be used with the consent of Oracle support, and this parameter should NOT ever be set in Oracle 12c.

SQL> select event from v$session_wait where event not like 'SQL%' and wait_class <> 'Idle';

kksfbc child completion
kksfbc child completion
kksfbc child completion
kksfbc child completion

Bug 6795880 - Session spins / OERI after 'kksfbc child completion' wait

A session may go into an infinite spin just after a wait for 'kksfbc child completion'. The spin occurs with a stack including kksSearchChildList -> kkshgnc where kksSearchChildList loops forever.


  Fixes for this bug in 10g and 11gR1 are disabled by default.

  To enable this fix you must explicitly set the following  parameter for instance startup:

    "_cursor_features_enabled" = 10



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