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Home -> Community -> Mailing Lists -> Oracle-L -> Parallelizing RMAN Backup
Peter :
I have seen this statement it in a couple of places.
The first reference is straight from the horses mouth (not the first time
Oracle's doc has been wrong).
If you took the "Oracle 8i Enterprise DBA Part 1B: Backup and Recovery
class" - refer to page 12-27 - under 'Parallelization of Backup Sets'. Here
it states :
If FILESPERSET is not specified, only one channel is used to create one
backup piece containing all files - all other channels remain idle.
I recently came across it in a white paper by Howard Rogers. You can see the paper at : http://www.vampired.net/articles/php/backup.php Download the paper called : Backup and Recovery by Howard Rogers Refer to page 62. Titled : 11.2.1 Parallelism There you will see the following reference ; If you didn't use this line (FILESPERSET), the in fact the entire backup would be undertaken by channel 1, and the other two would sit idle.
I believe that I have seen this referenced somewhere else but can not seem to find the reference right now.
This contradicts what the 8i RMAN manuals are saying (see below). I was wondering if this was an 8.0 bug that Oracle got rid of in 8i OR is it true ?
Peter Gram wrote:
Hi Pat
I don't know where you got the information on the Rman will not parallel the backup without using the filesperset parameter. I only use the filesperset parameter when backing up archive files. It is the allocation of multiple channels that determinate if it is possible to do backup's in parallel.
Pat Howe wrote:
I am researching RMAN and I am trying to understand how to parallelize the
backup.
I have come across the following statement in various papers and in the 8i
Backup and Recovery Course Material :
It is important to set FILESPERSET in the backup.
This will ensure that each allocated channel only processes the specified
number of files.
If you DO NOT specify FILESPERSET then the backup would only be undertaken
by "1 channel" and "all other allocated channels would sit idle".
Yet in the "8.1.6 RMAN User's Guide and Reference" it contradicts this (pg 1-31) :
The number of channels that you allocate affects the degree of parallelism
within the command.
RMAN internally handles parallelization. You only need to specify :
> 1 'allocate channel' command
The objects that you want to backup
Parallelism is exploited only within the context of a single command.
So it does not mention that you HAVE TO specify the FILESPERSET statement.
On digging further into the FILESPERSET statement the manual states (pg
1-36) :
The default value of this parm is calculated by RMAN as follows ;
RMAN takes the lower of the following 2 values ; 64 or
number-of-files/number-of-channels.
Page 1-37 gives an example of using the Default FILESPERSET - and how RMAN would parallelize the backup.
Which is right ?
Do you have to specifically specify the FILESPERSET parm in the BACKUP
command for RMAN to parallelize the backup operation?
or
Can you leave it out of the BACKUP command and use the default value ?
Thanks in advance_________________________Patrick J. Howe
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Pat Howe INET: phowe_at_Illuminet.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Fri Mar 01 2002 - 10:48:29 CST
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