Oracle-L: Re:Hot Backup using EMC /BCV splits

From: <dgoulet_at_vicr.com>
Date: Thu, 15 Aug 2002 07:23:39 -0800
Message-ID: <F001.004B61B8.20020815072339@fatcity.com>

Nate,

We are using EMC and BCV's each night to create both backups and a reporting database. Your SA has it WRONG.

Put all tablespaces in hot backup mode
sleep 5
split the bcv
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.

Dick Goulet

____________________Reply Separator____________________
Author: "Nat" <nat2710_at_hotmail.com>
Date:       8/15/2002 6:58 AM

Hello,

We are on IBM AIX 4.3.3 with EMC and BCVs. Our Unix admin has setup the backups for the database in following sequence to do the Hot backup.

Put all tablespaces in the database in Hot backup mode
Sleep 5
Put all the tablespaces back into normal mode
Split the BCV's
Mount on another machine and backed up from it.

What I am concerned is with step 4. Split BCV's should be done at step 2 instead of step 4.
According to our Unix Admin, EMC takes care of consistency and there is no need for any concern. As per him the split is instant split and EMC guarantees consistency.

What do you all think. What is the recommended procedure.

TIA, Nate

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Author: Nat
INET: nat2710_at_hotmail.com

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Author:
INET: dgoulet_at_vicr.com

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