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RMAN performance

Posted on 2012-03-19
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Last Modified: 2012-03-30
We have an ASM database on a P780 AIX with almost 72 data files and the DB size now is 200 GB
The backup started to take almost 3 hours the I have started to allocate 16 channels as following

RUN {
allocate channel d1 type disk ;
allocate channel d2 type disk ;
allocate channel d3 type disk ;
allocate channel d4 type disk ;
allocate channel d5 type disk ;
allocate channel d6 type disk ;
allocate channel d7 type disk ;
allocate channel d8 type disk ;
allocate channel d9 type disk ;
allocate channel d10 type disk ;
allocate channel d11 type disk ;
allocate channel d12 type disk ;
allocate channel d13 type disk ;
allocate channel d14 type disk ;
allocate channel d15 type disk ;
allocate channel d16 type disk ;
backup check logical as compressed backupset tag='DBPRO_rmanbackup_compressed'
database filesperset 1 plus archivelog;
crosscheck backupset;
crosscheck copy;
crosscheck archivelog all;
delete noprompt expired backup ;
delete expired archivelog all;
delete noprompt obsolete;
}


How can we improve this to be faster ?
Can we use maxopenfiles here?
Is using filesperset 1 correct here?
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Question by:it-rex
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by:slightwv (䄆 Netminder)
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Do you need to do a full backup every night?

I would suggest a rolling incremental with block change tracking:

4.4.3 Incrementally Updated Backups: Rolling Forward Image Copy Backups
http://docs.oracle.com/cd/B19306_01/backup.102/b14192/bkup004.htm

Then only blocks that have changed are backed up and the incremental is merged back into your level 0 (full) so you always have a full around.
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by:it-rex
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what if I want to improve this full backup.
before it used to be 1 channel and took 4 hours now with 16 channel  it went down to 1 and 40 minutes,I think we can do more.

thanks
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by:slightwv (䄆 Netminder)
slightwv (䄆 Netminder) earned 200 total points
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I've not messed a lot with tweaking a multiplexed backup.  I just do the rolling incremental and let RMAN take the defaults.

I would suggest you refer to the docs to answer your questions:

http://docs.oracle.com/cd/E11882_01/backup.112/e10642/rcmcncpt.htm#autoId15

Hopefully another Expert will stop by later that has done this.
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MikeOM_DBA earned 200 total points
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...with almost 72 data files and the DB size now is 200 GB
That is an average of less than 3 GB per file!
Definitely try using a larger "files per set", perhaps 24 or more.

And if you have enough backup space, consider an "image copy" with daily incrementals.
Or...do the rolling incremental with block change tracking as slightwv suggest.

Also, instead of continuing to increase the number of data files in the database, increase the size of the existing files!
;)
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by:schwertner
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I guess you have reached the optimal speed of the backup for this 200 GB database.

To increase the speed use something like:

database filesperset 4

Next suggestion (if you can use independent devices outside the ASM):

Distribute the files accross devices:

http://www.dba-oracle.com/t_rman_distribute_backup_files.htm
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by:it-rex
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Thanks all
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