Re: FTS, db file sequential read on undo

  • From: Scott <oraracdba@xxxxxxxxx>
  • To: vbarac@xxxxxxxxxxxx, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
  • Date: Mon, 13 Apr 2009 10:43:40 -0700 (PDT)

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@xxxxxxxxxxxx>
To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
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
Thanks for all insights,
Vladimir Barac
Database administrator | Alghanim Industries
P.O. Box 223 , Safat 13003 , Kuwait
Tel: +965 1881 111  / ext. 2960
This e-mail message and any attachments to it are for the sole use of the 
intended recipients and may contain confidential and privileged information.  
This e-mail message and any attachments are the property of Yusuf A. Alghanim & 
Sons w.l.l. or any of its subsidiaries or affiliates (“Alghanim Industries”).  
Any unauthorized review, use, disclosure, or distribution of this e-mail 
message or its attachments is prohibited.  Any opinions expressed in this 
message are those of the author and do not necessarily reflect the opinion of 
Alghanim Industries.  If you are not an intended recipient, please notify the 
sender by reply e-mail and destroy all copies of the original message and any 


Other related posts: