RE: ORA-1555 error with AUM already enabled
- From: "Newman, Christopher" <cjnewman@xxxxxxxxxxxxx>
- To: "'janine@xxxxxxxxxx'" <janine@xxxxxxxxxx>, oracle-l L <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 25 May 2010 17:26:29 -0500
Add some more undo datafiles and increase your retention period; 900 = 5
minutes which isn't long enough :) Here's a lil blurb from the docs:
Specifies (in seconds) the amount of committed undo information to retain in
the database. undo_retention can be used to satisfy queries that require old
undo information to rollback changes to produce older images of data blocks. A
setting of 7200 = 2 hours, 10800 = 3 hours, 14400 = 4 hours, 18000 = 5 hours.
The undo_retention works best if the current undo tablespace has enough space
for the active transactions. If an active transaction needs undo space and the
undo tablespace does not have any free space, then the system will start
reusing undo space that would have been retained. This may cause long queries
to fail. Be sure to allocate enough space in the undo tablespace to satisfy the
space requirement for the current setting of this parameter.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Janine Sisk
Sent: Tuesday, May 25, 2010 5:22 PM
To: oracle-l L
Subject: ORA-1555 error with AUM already enabled
A full export of my database takes far longer on AWS than it does on my old
Linux server (30 minutes vs 2+ hours). During the export, I receive the
following error:
EXP-00056: ORACLE error 1555 encountered
ORA-01555: snapshot too old: rollback segment number 1 with name
"_SYSSMU1_3780397527$" too small
I checked the parameters that control automatic undo management and found them
to be set correctly:
SQL> show parameter undo
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
undo_management string AUTO
undo_retention integer 900
undo_tablespace string UNDOTBS1
I tried running the export again, to see whether Oracle would have
automatically adjusted something to fix the problem, but it failed again.
Is this just one of those freak cases where circumstances have psyched out the
automatic feature, or is there something I can do to fix it, beyond whatever
the manager is doing? Clearly the immediate problem is that my rollback
segments are too small, but since Oracle is managing them I hesitate to go make
them bigger myself. The longer range issue is the slow performance of the
virtual disk drives, which is something I haven't delved into yet.
thanks,
janine
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