RE: RMAN backup to tape and blksize

I'm following as outlined in the Tuning Oracle Recovery Manager paper: Increasing BLKSIZE When Backing Up to Tape The RMAN channel parameter BLKSIZE defines the size of the tape buffers. Our testing shows that the size of tape buffers should be at least 256 KB. In some cases, even larger values improve performance.

Tables 11 and 12 shows how Oracle8i performances are improved by 20% by increasing the size of tape buffers to 256KB.

You can change the size of each tape buffer with the PARMS parameter of the ALLOCATE CHANNEL or CONFIGURE CHANNEL command. If the BLKSIZE parameter for PARMS is supported on your platform, then you can set it to the desired size of each buffer. For example, to set tape buffer size to 512 KB, configure an SBT channel as follows: CONFIGURE CHANNEL DEVICE TYPE sbt PARMS="BLKSIZE=524288"; It is also covered in Oracle Recovery Manager: Performance Testing at Sun Customer Benchmark Center

• We used the BLKSIZE parameter to set the RMAN tape buffer size to 1 MB. • We set the physical tape block size to 1 MB by entering 1048576 into the VERTIAS NetBackup configuration file
/usr/openv/netbackup/db/config/size_data_buffers.

and later in the same paper:
The Oracle9i RMAN configuration was straightforward and looked as follows: CONFIGURE DEFAULT DEVICE TYPE TO SBT;
CONFIGURE DEVICE TYPE SBT PARALLELISM 40; CONFIGURE CHANNEL DEVICE TYPE SBT MAXOPENFILES=1 PARMS='BLKSIZE=1048576, ENV=(NB_ORA_CLASS=Oracle_backup)' FORMAT '%U_%t';
VERITAS NetBackup Configuration
We used the default VERITAS NetBackup Configuration except for increasing the VERITAS NetBackup tape block size to 1 MB in the file /usr/openv/netbackup/db/config/size_data_buffers. The default VERITAS NetBackup tape block size is only 64 KB, which did not give acceptable performance.

Now, to my understanding the blocksize must be set at the rman side as well as the MML side. Setting it at the rman command line takes care of sizing the output buffer size. We use Netbackup and I'm told that the version we use set the blocksize dynamically and despite my wishes the SA is unwilling to make the change to enforce that it be 1MB. I do still want to ensure though that I'm passing the MML 1MB and see if the backup time changes. Unofrtunantly I won't be able to tell what the MML does on that end.

-- 
..
David



>> -----Original Message-----

>> Can someone please shed some light on how to pass the blksize

>> parameter to rman on the channel allocation?

>

> I am curious as to which media managment software requires this parameter.

> As far as I know, media management software handles tape however it

> handles

> tapes.

>

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