Re: ORA-01555 on source database for materialized view refresh across link

On Mon, 23 Jan 2006 21:59:28 +0000, Chuck wrote:

> Size of the undo_ts in this case is irrelevant if as you say it never
> gets > 50% full.
>
> If your undo_ts is large enough to hold 2x undo_retention at peak undo
> rate, the TS will never get > 50% used. If you are getting ora-1555 it
> is probably because undo_retention is set too low.
>
> How long have the queries on dbA been running when they fail? Probably
> longer than undo_retention.

Contrary to the popular opinion, size does matter. If you set UNDO_RETENTION to 3 days, Oracle will try protecting undo blocks for 3 days before allowing you to reuse them. In order for that war on ORA-1555 to succeed, you must have enough fresh blocks so that the previously used blocks are kept in the frig for 3 days. That's how size comes into the play.

-- 
http://www.mgogala.com