Re: Question: Backing up online databases

From: <jl34778_at_corp02.d51.lilly.com>
Date: 8 Nov 94 20:05:49 EST
Message-ID: <1994Nov8.200549.1_at_corp02.d51.lilly.com>

>> Now then, If you can't back up the redo logs, then what does that mean will
>> happen when the system crashes and I have to restore?
>>

Actually, you don't need to backup your redo logs. The process goes something like this:

0. You have to be in ARCHIVELOG mode to do this at all...
1. Set BEGIN BACKUP for a tablespace
2. Back up the tablespace
3. Set END BACKUP for the tablespace
4. Continue with 1-3 until you have done all tablespaces
5. Back up the control file
6. Back up the log files, just to get the file names and sizes.
7. ALTER SYSTEM SWITCH LOGFILE
8. Back up the archived redo logs.

The basics of a recovery goes like this: (I apologize if I miss a step, it has been a while since we last tested this process.)

1. Restore all of the tablespace files, control files, redo logs, and archived redo logs.
2. STARTUP MOUNT the database
3. SET AUTORECOVERY ON
4. RECOVER DATABASE USING BACKUP CONTROLFILE;
5. ALTER DATABASE OPEN RESETLOGS;

Because you did an ALTER SYSTEM SWITCH LOGFILE after the backup, all of the log information that you need has been archived. So, you don't need what is in the 'real' redo logs. That is also why you do a RESETLOGS.

Hope this helps. We have tested this process a number of times, and have had to recover using this process. Works like a charm.

-- 
Bob Swisshelm                | swisshelm_at_Lilly.com     | 317 276 5472
Eli Lilly and Company        | Lilly Corporate Center  | Indianapolis, IN 46285

Received on Wed Nov 09 1994 - 02:05:49 CET