RMAN took 12hrs to restore

Last week, I had to perform recovery on a unix database using RMAN...
My only concern about this whole recovery is the fact that it took RMAN 12hours to restore the 150gb files from tape. In the previous mock recoveries, the restores has taken about 3 hours maxium. I couldnt figure out why it took to much time.. everything is the same. the data has grown by 15%. The hotbackup takes about 3.5hrs to backup at incremental 0 (full). Can you kindly make some suggestions?

The following is my rman script
Run {
set until logseq 43111 thread 1;
allocate channel 'dev_0' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_1' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_2' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_3' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_4' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_5' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_6' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_7' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_8' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_9' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
connect target trxp
restore controlfile;
alter database mount;
restore database;
recover database;
}

You appear to be allocating waaay too many channels. Generally speaking, 2 ought to suffice. Look at the RMAN user guide on how this might affect backup/recovery performance.

Just to backup (get it!) what Axr2 said, I started adding more channels to my backups to find the optimal setting. Three channels was great but when I added a fourth, performance got worse. We didn't have the bandwidth to support it

I agree with Hacketta1 & Axr2. That's way too many channels. Did it actually use all of them? Do you have that many devices in your tape system? RMAN should only use as many channels as devices available.

Another possibility - was anything else going on on your tape system at the same time? Other systems backing up? Reclimation? System level backups?

Whenever I have to restore, I always make sure my tape system stops all other processes for the duration of the restore.

Jodie

so what you are really saying is that by over allocating more channels, I can actually slow down the rman restore? howz that possible? can somebody explain me that?

Quote:

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Originally posted by jlakhani
so what you are really saying is that by over allocating more channels, I can actually slow down the rman restore? howz that possible? can somebody explain me that?

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They will compete for bandwidth. Can you answer some of my questions? Were all the channels used in the restore? Do you have that many tape devices? Was anything else being done on the tape system at the same time?

You need to benchmark backups with different channels... take the size of the backup file divide by the time it took to back up. Do this for each piece that is backed up (i.e channel). Sum it up for all the pieces. You will get your throughput and you can see what is optimal. You may get 10M a minute with 2 channels, but only get 7M a minute with 3 channels, etc. I'd use the same for restore that I used to back up. How many do you use on your daily backups that take 3 hours?

Also, a restore WILL take longer than a backup... and depending on how many archive logs you have to restore, that will add time too. But it shouldn't be 4x.

Lastly, there could be a problem with your tape system. I have had to do a few restores here, and every once in a while, I will watch how much data is coming across, and I'll get like 30 MEG in 1 hour. It's weird. I stop and start the restore, and it flies. Nobody here knows why, and I know how to fix it, so if I see it I just stop it and start over. So I would watch the restore rate to see if you have some problem there too.

HTH
Jodie

Quote:

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so what you are really saying is that by over allocating more channels, I can actually slow down the rman restore? howz that possible? can somebody explain me that?

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Quote:

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Look at the RMAN user guide on how this might affect backup/recovery performance.

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The RMAN User guide explains it quite nicely. Take the time to read it.

Jodie,
I dont think all the channels were used for the restore. they configured 2 tapes to work with this backup via Omniback 4:data protector. So I used the restore command directly from the Omniback Specs...

Quote:

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Originally posted by jlakhani
Jodie,
I dont think all the channels were used for the restore. they configured 2 tapes to work with this backup via Omniback 4:data protector. So I used the restore command directly from the Omniback Specs...

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If you have only 2 tape devices - don't bother configuring more than 2 channels. Adding more only helps if your restoring from disk. I'd still check to see if anything else was running at the same time.

Good Luck.
Jodie

How many more channels would you recommend? I read somewhere on metalink that for Omniback it requires 4 channels and doesnt use more then 4 channels..

Quote:

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Originally posted by jlakhani
How many more channels would you recommend? I read somewhere on metalink that for Omniback it requires 4 channels and doesnt use more then 4 channels..

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I don't know anything about Omniback, but if you only have 2 devices, I wouldn't think you would want anymore than 2 channels.

You can always test it out. Configure 4 channels, run a backup, and see how many channels are used. If you look at the output of your backup, it will tell you which channels are used. It may "allocate" 4 channels, but see how many are actually used at one time. Then run it with 2 and then 1 channel. Look at your times and your throughput.

Like slimdave and Jeff always say... you need to benchmark!

Good Luck!

Like Jodie said, you may well have something else happening with your tape device... I did an adhoc backup a while back before a major DB change and left it to play golf for a couple of hours (ahem... hope my boss doesn't read this, I was claiming overtime...). When I came back, it had only done about 1% of the backup because the cleaning tape was trying to eject one of my tapes as part of a scheduled maintenence routine. Once I stopped the maintenence plan, the backup flew.

I am going to use 4 channels to do a backup and see how fast that runs.. Also, if I wanted to restore RMAN to a different location/Server then do you have a suggestion on how I can do that?

thanks
Jigar

http://metalink.oracle.com/metalink/...T&p_id=73974.1

You see this is our current rman scrpt: We are doing an incrimental 0 backup
Question 1: If I use backup database or backup full command rather then backup incremental level filesperset 1 will my backup/restore run faster?

Question 2: Currently my fileperset is 1 for 116 datafiles. If i change that to 52 which is half of 116 then will all the channels be utilized? What if I dont specify a fileperset..will rman figure out he fileperset? Omniback limits fileperset to 1..

allocate channel 'dev_0' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_1' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_2' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_3' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_4' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_5' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_6' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_7' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_8' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
allocate channel 'dev_9' type 'sbt_tape'
parms 'ENV=(OB2BARTYPE=Oracle8,OB2APPNAME=trxp,OB2BARLIST=TRXP_RMAN_Online)';
backup incremental level filesperset 1
format 'test_rman.dbf'
database
include current controlfile
;
}

Quote:

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Originally posted by jlakhani
You see this is our current rman scrpt: We are doing an incrimental 0 backup
Question 1: If I use backup database or backup full command rather then backup incremental level filesperset 1 will my backup/restore run faster?

Question 2: Currently my fileperset is 1 for 116 datafiles. If i change that to 52 which is half of 116 then will all the channels be utilized? What if I dont specify a fileperset..will rman figure out he fileperset? Omniback limits fileperset to 1..

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Question 1 - Backup database and backup incremental 0 are the same except one can be used in an incremental restore, the other can't. I'll let you guess which one is which! :)

Question 2 - I feel like I'm talking to a brick wall here. You can only use as many channels as you have tape devices. Like I said, I know nothing about Omniback, but that's the way it works for all the other media managers I know about.

I did search google a bit for your problem (You may want to try that too!) A quick look and I found that Omniback DOES appear to limit filesperset to 1. (A MAJOR downfall in my opinion) So if that's the case, and you have 116 datafiles, each backup will consist of 116 pieces. If you open 1 channel, it will back up 1 at a time. If you use 2 channels, you can finish in roughly half the time since you are backing up 2 files at the same time - assuming your bandwidth can handle it. Using more channels is a WASTE since you only have 2 devices!!!!

Another thing I found in my google search is that omniback implements a wait between each file when doing a restore. (Another downfall in my opinion). The poster (on the IOUG Forum) said that after tweaking some parameters, he got the wait down to 1-1.5 minutes. That means by default, this must be higher. So, with your 116 files, your looking at ~3 hours of wait time on a restore - at least. OUCH!

All of my opinions are based on my experience which has nothing to do with Omniback. I highly suggest you read (or re-read) the RMAN Users guide and find some good documentation for Omniback! You should also start paying close attention to the output of your backups and restores so you can see exactly what is happening. Watch the output as the backups, etc are happening. You might be surprised at what you learn... like what channels are restoring what pieces and in what order.

Good Luck
Jodie