异常等待事件：kksfbc child completion

今日巡检的时候发现有一套数据库中有"kksfbc child completion"的等待事件，过去没见过，查了下MOS发觉是一个BUG，记录下：

Bug 6795880 - Session spins / OERI after 'kksfbc child completion' wait - superceded [ID 6795880.8]

Affects:

Product (Component)	Oracle Server (Rdbms)
Range of versions believed to be affected	Versions BELOW 11.2
Versions confirmed as being affected	11.1.0.6 10.2.0.4 10.2.0.3
Platforms affected	Generic (all / most platforms affected)

 Note that this fix can cause / expose the problem described in Bug:8575528 



 Note that this fix has been superceded by the fix in Bug:8575528 

Fixed:

This issue is fixed in

11.1.0.7 (Server Patch Set) 10.2.0.5 (Server Patch Set) 10.2.0.4 Patch 5 on Windows Platforms

官方描述：

This fix has been superseded by bug:8575528.
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.
This problem can also lead to internal error such as any of
ORA-600 [kksSearchChildList1], ORA-600 [kksSearchChildList2]
ORA-600 [kksSearchChildList3], ORA-600 [kkshgnc-nextchild]
Or Trace dumps on kksSearchChildList4 .
Note:
  This fix is disabled by default in 10g.
  To enable this fix you must explicitly set the following
  parameter for instance startup:
  _cursor_features_enabled = 10

可以通过设置_cursor_features_enabled参数为10来解决该问题，但是设置该参数需要重启数据库。