Bug 7291739  Contention with auto-tuned undo retention or high TUNED_UNDORETENTION

 This note gives a brief overview bug 7291739. 
 The content was last updated on: 18-NOV-2010
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Affects:

Fixed:

Description

High 'latch: row cache objects' contention may be seen on dc_rollback_segments

together with high 'enq: US - contention' waits when using system managed undo

with an auto tuned undo retention period.

As another aspect, long running query can raise tuned_undoretention to

very high value and exhaust undo tablespace resulting in ORA-1628.

This fix allows users to specify a high threshold for undo retention via

the "_highthreshold_undoretention" parameter. The tuned value of undo retention

will then not exceed the set value. This underscore parameter is a dynamic

parameter and its value can be changed with

  "alter system set "_highthreshold_undoretention"=;"

Workaround:

  Disable auto tuning by setting "_undo_autotune" = false

Note:

  One off patch on 10.2.0, including PSU 10.2.0.4.4 and later will use parameter

  "_first_spare_parameter" instead of "_highthreshold_undoretention"

  Please see patch readme for detail.

References

Bug:7291739 (This link will only work for PUBLISHED bugs)
Note:245840.1 Information on the sections in this article