Shutdown Immediate Hangs: Common Causes [ID 106474.1]

Shutdown Immediate Hangs: Common Causes [ID 106474.1]
	Modified 13-JUL-2007     Type PROBLEM     Status PUBLISHED

 

Problem Description

-------------------

 

Shutdown immediate hangs or goes very slowly.  You can shutdown abort

with no problem.

 

 

Solution Description

--------------------

 

There are two common causes of a shutdown immediate hanging.

These are:

 

   Rollbacks

   Temp segment cleanup

 

 

Explanation

-----------

 

Rollbacks: If a large dml statement is in progress it must roll back before

the shutdown completes.  In pre 8.1 versions of Oracle this can

be made to go faster with a higher cleanup_rollback_entries, but

be careful because too high a setting can cause resource contention

during normal database operation.

 

Temp segment cleanup:  If your tablespace used for temp sort segments

is of type temporary (as shown by the CONTENTS column of DBA_TABLESPACES)

the extents, once allocated, are never deallocated until shutdown. 

Instead they are tracked in the SGA.  This helps reduce dictionary

cache contention during normal database operation.  Unfortunately,

when we shutdown these extents must all be deallocated at once which

can lead to the dictionary cache contention we avoided while we were

running.  The tablespace of type temporary was introduced in 7.3.

 

These two problems can also combine to make things even slower as a

rollback will also deallocate extents, leading to further contention

on the parts of the dictionary cache that track used and free extents.

 

 

References

----------

 

Note:1060831.6 cleanup_rollback_entries

Note:73439.1   Temporary Segment Handling

 

 

 

 

 

 

 

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