RE: ORA-01555 seems bogus
Date: Sun, 7 Feb 2010 12:20:28 -0500
Message-ID: <0EB816E9589B431AAEAA6B7F7569FE71_at_rsiz.com>
What is updating the 3100 row table? What is the commit frequency? Is something doing an uncommitted update, a wait, and then a rollback? Does the frequency occurrence of the 1555 plausibly overlap with rollbacks? I haven't checked yet, does dba_tab_modifications get hit only on commit? I'm afraid I don't have your version handy to test.
The test of course could be very simple, just create a junk table, put a row in and commit, check dba_tab_modifications, update with no commit, check dba_tab_modifications from another session, rollback, check dba_tab_modifications again. Maybe the test could be even simpler but I didn't have time to think it through much.
Good luck,
mwf
-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]
On Behalf Of Herring Dave - dherri
Sent: Saturday, February 06, 2010 10:10 PM
To: oracle-l_at_freelists.org
Subject: ORA-01555 seems bogus
Folks, I've got a curious situation where we're getting regular ORA-01555 errors yet they don't seem correct. First a few things on the set up:
- 4-node RAC (+ 4-node RAC DG)
- 10.2.0.2
- RHEL 8 x 64GB servers
The query returned in the error is doing a full scan of a 3,100 row table, which takes less than 1 sec to complete. I've tried the same query repeatedly and it always takes less than one second, even when trying it while ORA-01555 errors are being returned saying that query is failing elsewhere. The query is run 10,000+ times per day, always run from the same node.
The ORA-01555 error lists this query as having a duration of around 12,000 seconds each time, which from what I can tell is impossible. Again, it's a 3,100 row table, no parallelism, 1 index (which isn't used by this query). I checked LAST_ANALYZED and the table hasn't been analyzed in 4 days. I checked DBA_TAB_MODIFICATIONS and it's had around 200 DML's since it was analyzed, but the last of which was 2 days ago.
So is Oracle returning the wrong query? Is the ORA-01555 bogus? Checking GV$UNDOSTAT, SSOLDERRCNT matches the # of ORA-01555 we're seeing (87 today, all the same query). All instances have the same UNDO_RETENTION (3600) and similarly sized undo tablespaces.
Any clues how to catch the trouble making queries?
Dave Herring | DBA, Global Technology Services
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