Re: FTS, db file sequential read on undo

Depending on the version you may have hit a bug. Sequential reads are a normal process but in some cases such as this it could be do to a bug. There are several bugs that can cause higher than normal sequential reads.

Index truncates/rebuilds -- Bug 6455161
Delayed block cleanouts -- Bug 8410146

and not a bug but row chaining can be an issue as well.





________________________________
From: Vladimir Barac <vbarac_at_Alghanim.com>
To: "oracle-l_at_freelists.org" <oracle-l_at_freelists.org>
Sent: Monday, April 13, 2009 9:36:12 AM
Subject: FTS, db file sequential read on undo

 
Hello, listers
 
We are facing rather strange situation…
When accessing table for analyze or to export table, we
are seeing "db file sequential read" wait event. V$session_wait file#
is 2, that is – UNDO tablespace. Because of this analyze or export take
forever to complete.
 
Why would analyze or export access UNDO tablespace? There
are definitely no transactions at all on the system going on at the time of
export/analyze.
 
Thanks for all insights,
Vladimir Barac
Database administrator | Alghanim Industries
P.O. Box 223 , Safat 13003 , Kuwait
Tel: +965 1881 111  / ext. 2960
 
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