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What does it mean media is assigned ? Can't two different policies write to the same media ?

Dear all , 

  I need to understand a point here on Netbackup

I wanted to test a new policy I have added and I directed the policy to use a media pool which already have only one tape and have been used by another active policy the thing is that the backup job failed several times with the code 96  no media available however I'm sure that the tape is there and available and have enough space to take the required backup. 
Then I searched through my media tapes and checked all tapes available until I found one tape which didn't have its time assigned coloumn populated which , only this tape was able to be used

Can I understand why ? why couldn't I use the same tape for two different policies ? What does this coloumn time assigned means ? 

Appreciate your reply

 

1 Solution

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Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

Technically, a tape is 'assigned' when it has an entry in the 'media DB' - eg. bpmedialist -m <media id> returns valid output.

In the vast majority of cases, this means the tape contains images, or the first image is currently being written and is not yet complete.  Or, the images on the tape have just expired, and the tape is waiting to be cleaned up via the NBU image cleanup processes.

Just occassionally, a tape can be left assiged with no images - if the tape becomes frozen for example due to a fault, before the first image is successfully written, you now have a tape with no images that is assigned ...

 

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Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

A allocated media means the tape has active backup on it. One policy will be able to use the same tape from another policy if:

  • volume pool is the same
  • retention level (backup life time) is the same.

 A tape without a assigned time is likely a scratch (free) tape.

do you have a scratch pool defined ?

Background info about scrtch pools: http://www.veritas.com/docs/000124735

Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

Media assigned: Media is taken to something. The policy allow to use the media. We have Month-backup, Year-backup and all schedules that have monthly backup goes to tape. 

If you like you can check out SLP (storage lifecycle policy), for more advanced feature.

happy backup. 

Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

but actually there was no active backup on it or do you mean active images 
Also it's worth mentioning that  there may have been an active backup going on but it either finished or canceled so eventually there is no real active backup going on or does it take time to reflect that on the media ? 

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Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

no I don't have sratch pool 

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Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

if you add tapes to the scratch pool it will automatically take tape and assign them accordanly. 

Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

Please show us output of these commands from cmd:
In ...netbackup\bin\goodies:
available_media

In ...netbackup\bin\admincmd:
bpmedialist

bppllist (policy-name) -U

Please copy the text output and post here.

Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

@Mahmoud_Moussa

Please post text output of commands that I have requested yesterday?

Nicolai's reference to "allocated media means the tape has active backup on it" means valid, unexpired backup image(s), that probably has different retention level.

NBU does not mix retention levels on media.
It can be enabled but is NOT recommended.
The reasons can be found in numerous discussions in this forum.

Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

I will expand on the answers given.

A tape that has an assigned time 'probably' contains backups, but not 100% guaranteed.

A tape has an entry in what we refer to as the volume database, and the media databse.

Once a tape in known to NBU (appears under media in the GUI) it will have a volume DB entry, though may not contain images.  It will always have a volume DB entry until the tape is completly deleted from NBU.  The corresponsing entry for the tape in the vol Db can be seen with vmquery -m <media id>.

If a tape is 'scratch' it will not have a media DB entry (bpmedialist -m <media id> will show no entries).  When a tape is selected for backup, it will be given a media DB entry, and also an assign time.   It does not yet have images on it as the backup hasn't started to write any data yet.  If all goes well, the backup will be successful and the tape will then contain images.

I would argue, that the presence of an assign time therefore only signifies that a tape has a media DB entry .(bpmedialist -m <media id> will return data).  It is however, reasonable to suggest that an assigned tape 'probably contains images' and mostly this is true.

If the backup fails, it is possible for a tape to be left assigened, with no images on it.  Likewise, when all the images on a tape expire, the tape will be left with an assign time, and no valid images for a short time until it gets ceaned up during the NBU image cleanup processes.

 Edit to add:  The media and vol DbB are all part of NBDB.  The terms relate back to when media servers contained their own entries about media, after NBU 6 it's all in EMM (Part of NBDB) located on the master.  The volume and media DBs therefore do not exsist as seperate entities, and are these days really just terms used to describe entries tapes have in NBDB.

Accepted Solution!

Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

Technically, a tape is 'assigned' when it has an entry in the 'media DB' - eg. bpmedialist -m <media id> returns valid output.

In the vast majority of cases, this means the tape contains images, or the first image is currently being written and is not yet complete.  Or, the images on the tape have just expired, and the tape is waiting to be cleaned up via the NBU image cleanup processes.

Just occassionally, a tape can be left assiged with no images - if the tape becomes frozen for example due to a fault, before the first image is successfully written, you now have a tape with no images that is assigned ...

 

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Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

I think @Nicolai  had given you the clues there.

This one and only one media had been used by another policy, so it's already assigned with say retention A, if now you want the other policy to use that media, you need to make sure it's also set to retention A. Otherwise it won't be picked up and will try to look for a second media.

To have the same media storing data of different retention, you can go to master server host properties -> Media -> Tick on "Allow multiple retentions per media". 

Re: What does it mean media is assigned ? Can't two different policies write to the same media ?

thanks all for your answers

I just needed to understand the term , the meaning of time assigned 

Appreciate all your efforts and explanation