Re: undo segments online causing performance problems.
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: "oracle-l" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 29 Dec 2005 14:15:57 -0000
The strategy with Automatic Undo is to have no more
than one transaction per undo segment if possible, which
is why Oracle keeps creating new ones if there is space
in the undo tablespace.
Have a check on v$resource_limit for resource_name =
'transactions'. The max_utilization column will tell you
the maximum number of concurrent transactions since
the database started up. The number of online undo
segments should not exceed. (Although there may be
a short period after restarting the database where that
is not true because of the number that are automatically
brought online at startup).
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
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----- Original Message -----
From: "The Human Fly" <sjaffarhussain@xxxxxxxxx>
To: "oracle-l" <oracle-l@xxxxxxxxxxxxx>
Cc: "Hemant K Chitale" <hkchital@xxxxxxxxxxxxxx>
Sent: Thursday, December 29, 2005 2:03 PM
Subject: Re: undo segments online causing performance problems.
I do have statspack report during this situation and what is mentioned
in the metalink note, exactly has been occured to us. Like, enqueue is
one of the top 5 timed events and under the enqueue activity, I see,
TX (transaction Exclusive) and US (Unod Segments) entries.
We have reported this to Oracle Support and they are still revieiwing
the TAR. My question, why oracle doesn't reuse the already online undo
in place of bring more undo segs. online.
Still puzziling.
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