10.2.0.4 11.1.0.7UNDO可能异常增大的BUG

表现为
 select tuned_undoretention from v$undostat;
的值异常大，UNDO_DATAFILE 不断的自动扩张。


mos有相关的BUG说明
Bug 7291739  Contention with auto-tuned undo retention or high TUNED_UNDORETENTION

Product (Component)Oracle Server (Rdbms) Range of versions believed to be affectedVersions BELOW 11.2 Versions confirmed as being affected

• 11.1.0.7
• 10.2.0.4

Platforms affectedGeneric (all / most platforms affected)

     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.

Workaround Disable auto tuning by setting "_undo_autotune" = false

记录于此备查

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