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Re: ORA-01555

From: Tim Gorman <>
Date: Wed, 02 Jun 2004 12:19:14 -0600
Message-ID: <>


Steve Adams has a terrific explanation at "". At the bottom, he posts a series of scripts as a last resort on preventing the ORA-01555 error at the bottom of the page. The scripts are named "prevent_1555.sql", etc...

Curiously enough, I've posted some similar scripts (also named similarly) to prevent ORA-01555 errors at "" -- my scripts are named "prevent1555_ddl.sql" and "". I've some papers and presentations on ORA-01555 at "", as well as Dan Fink's excellent ground-breaking paper/presentation on rollback/undo.

You'll notice that the code and specific methods in Steve's scripts and my script are similar but obviously different. The similarities are in the names of the scripts and the basic underlying method. Since there's really only one way to do what they do, similarities are unavoidable. I flatter myself to think that it is two minds thinking alike, arriving at the same conclusion separately. What it means for you is two different sets of scripts ready to try out...

Hope this helps...


on 6/2/04 2:50 AM, Justin Cave (DDBC) at wrote:

> My hunch is that the export is not causing the error. Rather, other
> transactions are changing the data, and when the export process tries to
> reconstruct the state of the data when the export started, the old data
> is no longer available in the rollback segments. Assuming this is the
> case, assigning the export process to a larger rollback segment will
> have no effect.
> If you were on 9i, you could use automatic undo management to greatly
> simplify the problem. If you are stuck with manual undo management via
> rollback segments, you will have to figure out why the rollback
> information isn't available when your query needs it. It may be that
> you have very small rollback segments that wrap too frequently, so
> increasing the size of the rollback segments will help. It may be that
> you need to increase the optimal size of your rollback segments. It may
> be that you need more rollback segments. So many possibilities :-(
> If possible, can you run export when the database is less busy? Are you
> specifying that the export should be consistent on the command line? Do
> you actually need a consistent export?
> Justin Cave
> Distributed Database Consulting, Inc.
> -----Original Message-----
> From:
> [] On Behalf Of Computer Centre -
> Sent: Wednesday, June 02, 2004 2:27 AM
> Subject: (no subject)
> Dear All,
> We are getting the following error during database export.
> ORA-1555 :- snapshot too old.
> How to assign a big RBS to the export session.
> Thanks in Advance,
> Balu,
> Oracle DBA

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Received on Wed Jun 02 2004 - 13:16:00 CDT

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