Re: Question on RMAN restore from tape

Typo correction

"Channel 4 reads from LTO tape 2: Backupset 4 <<<< blocked because channel 2 already uses LTO tape 1" ... should be ...
"Channel 4 reads from LTO tape 2: Backupset 4 <<<< blocked because channel 2 already uses LTO tape 2" of course :-)

Best Regards
Stefan Koehler

Independent Oracle performance consultant and researcher Website: http://www.soocs.de
Twitter: _at_OracleSK

> Stefan Koehler <contact_at_soocs.de> hat am 19. Dezember 2019 um 11:58 geschrieben:
>
>
> Hello Andrea,
> > In my experience, I see that rman will never tries to read the same "tape" in parallel. This is wise but this could limit your restore parallelism.
>
> This can happen very easily if you change the parallelism / amount of channels between backup and restore. I have seen this a lot of times with IBM TSM and physical LTOs for example and the client was wondering why increasing the amount of channels did not speed up the restore.
>
> Here is a simple example:
>
> Backup with 2 RMAN sessions (because backup SLA is not as strict as restore)
> -------
> Channel 1 writes to LTO tape 1 with: Backupset 1, Backupset 3
> Channel 2 writes to LTO tape 2 with: Backupset 2, Backupset 4
>
> Restore with 4 RMAN sessions (because restore SLA is more strict)
> -------
> Channel 1 reads from LTO tape 1: Backupset 1
> Channel 2 reads from LTO tape 2: Backupset 2
> Channel 3 reads from LTO tape 1: Backupset 3 <<<< blocked because channel 1 already uses LTO tape 1
> Channel 4 reads from LTO tape 2: Backupset 4 <<<< blocked because channel 2 already uses LTO tape 1

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