Re: Weird ORA-1555 error
Date: Wed, 28 Sep 2016 19:49:37 +0000
Message-ID: <TU4PR84MB0206BC87762689D799AB2625CCCF0_at_TU4PR84MB0206.NAMPRD84.PROD.OUTLOOK.COM>
Matt, have you checked v$transaction to see you have any several day old transaction such as caused by a dead front-end application where the Oracle session process is still in existence?
From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> on behalf of Matt Adams <MAdams_at_equian.com> Sent: Wednesday, September 28, 2016 3:23:58 PM To: Oracle L
Subject: Weird ORA-1555 error
I've seen ORA-1555 (snapshot too old) lots of times in the past and they always seemed to be caused by 1 of 2 scenarios.
Either an image of a block needed by a long running query is not available because another session has modified and committed a change to the block and the 'before modification' image of the block is no longer available in the rollback segments. (common) Or it's a delayed block cleanout issue where the ITL in the block header needs maintenance. (uncommon, but not exceedingly rare)
I'm now getting an ORA-1555 error that doesn't seem to fit either case.
This particular table is roughly 11 million rows in a database 10 terrabytes in size and not terrible busy. There's 300 Gig of undo tablespace and UNDO_RETENTION is set for 40 hours. (don't ask why 40 hours. I didn't set it up that way and nobody seems to remember why it was set that way)
Running the following query returns an error in anywhere from 2 to 10 seconds.
SQL> select count(*) from app_owner.type_history; select count(*) from hri1_owner.type_history
*
ERROR at line 1:
ORA-01555: snapshot too old: rollback segment number 491 with name "_SYSSMU491_93190984$" too small
The error is repeatable, with the same rollback segment (number 491) listed every time.
Since I'm getting this error in sometimes as little as 2 seconds or so, the first scenario I described above doesn't seem to apply.
Usually, the recommended action to eliminate problems with delayed block cleanout is to either gather stats on the table or do a 'select * from table' to force oracle to visit every block. That doesn't seem to be working here. All attempts to analyze the table or select count(*) from the table get the same ORA-1555 error
This is v 11.2.0.4 (EE) on solaris.
Searches on the web and metalink (yes, I still call it that) have proven fruitless so far.
Anybody have any thoughts on why this might be occurring?
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-- http://www.freelists.org/webpage/oracle-lReceived on Wed Sep 28 2016 - 21:49:37 CEST