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: @OracleSK
Stefan Koehler <contact@xxxxxxxx> 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
