Re: Oracle ORA-1555 Snapshot Too Old error

On Thu, 24 Oct 1996, Bert Evans wrote:

> "E. Fong" <efong_at_val.net> wrote:
>
> >I having a problems getting an ORA-1555 Snapshot too old error while trying
> reasons, ORACLE logs all of your transactions to the log file. When
> it fills one up, it starts using the next one. If you happen to fill
> up all of your log files, ORACLE attempts to resuse the first one.
> If, however, this log file is already being used by an uncomitted
> transaction, ORACLE has nowhere to write the new transactions and you
> will get the error you described.
>
> There are a number of things you can try:
>
> 1. Increase the size of your log files
> 2. Add additional log files
> 3. Modify your batch file so that it commits
> periodically while running. This can easily be done using
> a PL/SQL script like this:
>
> Bert Evans
> bevans_at_esper.com
>
>

#3 will help eliminate the ORA-1555. #1 and #2 really don't apply however.

The problem is with the rollback segments. In order to maintaing data consistency, a transaction may be required to read data from the rollback segments. Too many smaller transactions running concurently with the large transaction can cause the needed segment of the rollback to be written over, causing the ORA-1555.

It's detailed in the Concepts manual, chapter 10.

Jared Still
DBA
RxNet/ValueRx
jared_at_psnw.com Received on Thu Oct 24 1996 - 00:00:00 CEST