Re:Hot Backup using EMC /BCV splits

• dgoulet_at_vicr.com

> Nate,
>
> We are using EMC and BCV's each night to create both backups and a
> reporting database. Your SA has it WRONG.
>
> 1) Put all tablespaces in hot backup mode
> 2) sleep 5
> 3) split the bcv
> 4) return tablespaces to normal
>
> The reason that this is important has nothing in the world to do with EMC
> and everything to do with Oracle. Since switching the database files
> into and out of hot backup causes an immediate write to the file headers
> locking or unlocking the SCN. Consequently your backups are inconsistent
> and consequently worthless. The reason is that when you enter hotbackup
> mode all of the file SCN's are frozen giving Oracle a known starting
> point for recovery's sake. By switching back to normal mode the RDBMS
> has no idea of which transactions are in the files and which are not. It
> assumes that it is seeing an instance crash and will only use the on-line
> redo. Your DB will come up, but don't expect it to stay that way, ours
> crashed with "block corruption" 45 minutes later. Believe me, we tried
> it due to a misinformed EMC person(that doesn't happen does it?) & failed.

Problem there is that to get the oracle database that handles the export back online you have automate a recover until current (or check the current numbers and do a recover until the number).

Especially if the existing database is running parallel server and the new one isn't it's a pain.

Also: don't know if it's been cleared up in 9, but we used go through some gyrations to make the split off copy of the database use a different network name so that the backup server didn't come up answering the production database's queries.

Another luvly thing about the recover is that Oracle8 (may have changed) opens the redo's w/ O_READ | O_WRITE. If the production system exports them NFS read only (which makes sense to them) you have to copy the files locally in order to replay them. Doesn't sound like much but if you are trying to catch up to a heavily loaded database it can make a big difference.

The attached aren't the prettiest code in the universe but at least worked.

--
Steven Lembark                               2930 W. Palmer
Workhorse Computing                       Chicago, IL 60647
                                            +1 800 762 1582



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