RMAN Restore time

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03-25-2003, 12:30 PM
ocp8

RMAN Restore time

I am looking at implementing RMAN at my shop and have had numerous questions about the MTTR of our systems. I am facing a lot of resistance by people who are saying using RMAN will cause our downtown to be a lot longer than normal. On our HR system, for example, we would lay the hot backup files down and roll it forward. If I was to use RMAN with a weekly level 0 and incrementals during the week how much longer would it take to restore?? I do not have any practical experience with RMAN and I need to know this info if I plan on using it.
03-25-2003, 12:46 PM
adewri

Re: RMAN Restore time

Quote:

Originally posted by ocp8
I am looking at implementing RMAN at my shop and have had numerous questions about the MTTR of our systems. I am facing a lot of resistance by people who are saying using RMAN will cause our downtown to be a lot longer than normal.

Restoration with RMAN is no doubt much faster and automated than manual restoration provided that you have planned your backup strategy properly.

Quote:

On our HR system, for example, we would lay the hot backup files down and roll it forward. If I was to use RMAN with a weekly level 0 and incrementals during the week how much longer would it take to restore?? I do not have any practical experience with RMAN and I need to know this info if I plan on using it.

No need to bother about hotbackup, RMAN doesnot.

RMAN uses Oracle server processes to perform the reading of the database blocks from the datafiles, hence they are able to use the same read-consistency mechanism that SQL statements use.

RMAN records the SCN at the point-in-time the backup of the datafile started, in its own Recovery catalog in the control files, so there is no need to freeze the datafile headers. Without freezing the datafile headers and without the need for putting the tablespaces into backup mode, there is no longer any need for the ALTER TABLESPACE… BEGIN/END commands.

For more information

http://otn.oracle.com/docs/products/...a96566/toc.htm

HTH
03-25-2003, 01:08 PM
nagarjuna

We are testing RMAN. It took 9 months to convince my ppl :cool: It's been a smooth going (testing) sofar. We are using TDP as MML (it costs alot). We had initial hiccups in taking backup. Now, backups are OK. But, had problems in restoring few types of backups (with setlimit, maxbytes etc). RMAN/TDP bugs. Some how we managed to restore the backups. It took 8 hrs (with one channel) to restore our database of size 150GB (150GB occupied, 300GB allocated). Crossed the 1st hurdle of making RMAN/TDP work. Our next goal is tune the RMAN backup/restore. My statment is to go for RMAN. But, we need good practice before relying on it. Good pratice and good document abt how to restore in various cases. :cool:
03-25-2003, 02:06 PM
hacketta1

I'm no RMAN expert, only been using it a few months, but my understanding is this:

If you do a level 0 once a week, and a level 1 the rest of time, the level 1 and any level 0s that are needed will be restored. On the otherhand, if you do one level 0 once a week and level 1 cumulatives all the others days, when you recover you only need ever use the most recent level 1 and the most recent level 1 cumulative (for complete recovery, of course). Perhaps you could consider using the cumulatives. Hope this helps. Austin
03-25-2003, 02:08 PM
hacketta1

Quote:

use the most recent level 1 and the most recent level 1

Sorry, should read use the most recent level 0 and the most recent level 1
03-25-2003, 02:10 PM
marist89

Re: RMAN Restore time

Quote:

Originally posted by ocp8
I am looking at implementing RMAN at my shop and have had numerous questions about the MTTR of our systems. I am facing a lot of resistance by people who are saying using RMAN will cause our downtown to be a lot longer than normal. On our HR system, for example, we would lay the hot backup files down and roll it forward. If I was to use RMAN with a weekly level 0 and incrementals during the week how much longer would it take to restore?? I do not have any practical experience with RMAN and I need to know this info if I plan on using it.

You're comparing apples and oranges. If you are doing a full backup of your database via a hot backup, you should compare against a full database backup every day. If you are backing up to the same media (for example, DLT or AIT on both) there should be no significant difference in backup/restore times. However, RMAN has a unified interface (same across all platforms) so your DBAs don't have to know Legato for Unix, FooBackup for WindozNT, and EnterpriseFooBackup for W2K. Also, RMAN is supported by Oracle whereas your home-grown scripts are supported by you.
03-25-2003, 02:13 PM
marist89

Quote:

Originally posted by nagarjuna
But, we need good practice before relying on it. Good pratice and good document abt how to restore in various cases. :cool:

This is the step where most people fail in recovery scenarios. You need to DOCUMENT and TEST multiple recovery scenarios. Do not cut over to RMAN until you fully understand how to recover from three basic failures:
1. Loss of a control file
2. Loss of a filesystem
3. Complete Disaster
03-25-2003, 03:01 PM
nagarjuna

Quote:

Originally posted by marist89
This is the step where most people fail in recovery scenarios. You need to DOCUMENT and TEST multiple recovery scenarios. Do not cut over to RMAN until you fully understand how to recover from three basic failures:
1. Loss of a control file
2. Loss of a filesystem
3. Complete Disaster

Yep, that's what I meant by saying Good pratice and good document abt how to restore/recover in various cases :cool: