Re: Snapshot too old

On Sun, 02 Nov 1997 03:04:18 GMT, reberhard_at_interlog.com (Roberto Eberhardt) wrote:

>We constantly run into the ORA1555 error (Snapshot too old), to remedy this
>Oracle recommends increasing the size of the redo logs.
>
>This can be accomplished in two ways:
>1- Increase the size of individual segments
> or
>2- Increment the number of segments.
>
>Any suggestions on which one would be the most effective solution?

Hi Roberto,

the meaning of ORA-1555 is that a consistent read performed in charge of a query was unable to reconstruct the 'before' image from the rollback segments, because those data blocks were overwritten by undo data either from some other transaction or even from your own transaction. The latter case can happen if you are in a cursor loop which reads great amounts of data, and in that loop, you issue a commit. You should avoid such constructs. Some detailed explanation of Oracle concepts regarding consistent read and use of rollback segments can be found in 'Oracle Server Concepts Manual'. Info in Server Messages Manual for ORA-1555 may also be of use. Anyway, it has nothing to do with redo log configuration :-).

Hope this helps,
Peter

Peter Schneider
pschneider.ctj_at_metronet.de Received on Sun Nov 02 1997 - 00:00:00 CET