RMAN channel and streams at Netbackup end

[Kak4_12]

Hello Experts,

At script end DB team has set 2 channels but at Netbackup end RMAN backup completed successfully after generating 280 streams.

How Netbackup generates streams for RMAN backup and  is it mentioned anywhere that Rman backup will be complete after writing so many streams at nbu end?

[Nicolai]

With Oracle backup, the component in control is RMAN and it recover catalogue.

Netbackup is in Oracle terms a "media manager". A pipe to a storage medium. The media manger is the libobk library you are linking into Oracle.

RMAN sort a backup into backup piece and send the jobs off to Netbackup. Once Netbackup has saved the data (RC=0)  RMAN register this information into the RMAN catalogue. This is what it is essential to protect the recover catalogue. Netbackup as such as no idea of what backup images is required to restore a database. 

When it comes to restore, RMAN looks at the recover catalogue and select the backup piece required for a complete or partial restore. It doesn't necessary pick the same backup pieces from the same backup. So even a partial good backup will provide value for RMAN

Hope this clarify.

[StefanosM]

Netbackup does not generate oracle streams. Netbackup asks oracle to open two or more channels and oracle RMAN splits the backup into streams. How many streams appear and run  in the activity monitor is RMAN responsibility.

When the backup finish, RMAN informs netbackup that the backup is finished (ok or not). You can find this information at the RMAN script logs if you use rman script or in the activity monitor if you use oracle intelligent policies.

[Kak4_12]

Hello StefanosM

Is it mentioned in the RMAN script that these many streams have to  generated at the Netbakup end? Because i can see channels only in the RMAN script but i am not able to lovcate the no. of streams.

[StefanosM]

This is a question you have to ask a DBA. Netbackup is not responsible for the total stream number RMAN produces.

[quebek]

Hi
there is a setting called filesperset in RMAN. For the best dedup rates VRTS recommends to have it set to 1:

https://www.veritas.com/support/en_US/doc/16226115-151325417-0/v47472134-151325417

[StefanosM]

fileperset is not handling the stream initiation although is affecting the total number of streams.

Fileperset is a multiplexing factor for how many file-sets will go into one stream.

[davidmoline]

Hi @Kak4_12 

Re your comment "At script end DB team has set 2 channels" - this referes to concurrent streams (or parallel). So as the backup runs, you will only see two active jobs. How many streams in total are required will depend on a number of factors based on size what is being protected etc - as the others in this thread have indicated. 

Cheers
David