Use the same volume pool for two different policies

[Mahmoud_Moussa]

I have a netbackup environment 7.6.1
where I have two policies and only one volume pool with only one tape
Can I use the same volume pool the same tape for the two different policies or should I add one more tape ?

I'm asking because I get always an error 96 when one of the policies starts while the other policy is writing on the tape ?

Thanks

[Marianne]

If you have only one tape in the pool then all policy schedules using this pool must have the same retention level. How many tape drives? How many media servers? What is the MPX value in STU? What is MPX in the schedules of the policies? You may want to read up in Admin Guide II about how NBU selects media.

[Mahmoud_Moussa]

only one tape drive

only one media server

execuse me , what is MPX?

[Marianne · Accepted solution]

Multiplexing

Big question is retention levels in policy schedules... NBU does not allow mixed retentions on media.

[Mahmoud_Moussa]

so you mean that multiplexing should be allowed in addition to have all schedules with the same retention 

right ?

[mph999]

No, mpx does not have to be enabled.

Lets look at this another way, you have policy 1 and policy 2, these two policies contain one or more schedules.

Looking at policy 1, what is the retention period set in the schedule(s)

Then

Looking at policy 2. what is the retention in the schedule(s)

The retention period will be something like 1 week, or 2 months.

By default, NetBackup does not allow backups that have different retention periods to go to the same tape.

[Marianne]

As per Martin's reply - the answer is no. 

You don't need MPX to be more than 1.
It helps to write more than one job (from more than one client/job) to write to same tape drive and media simultaneously. 
See :

Example of using multiplexing with schedules : http://www.veritas.com/docs/000044532 

Please check retention levels in policy schedules (as per previous posts).

[Mahmoud_Moussa]

Thanks all 

I have checked the retention periods and I have made all of them the same which solved my problem 

Thanks again for your help

I also found an option when choosing the properties of the master server which enables mixing retention periods on the same media

I didn't choose it but I guess this would have helped also

Thanks again 

[Marianne]

Never a good idea to enable mixed retentions. This setting may fix the issue in the short term, but create more problems in the long run. When a mixed retention tape is full, you will need to wait for all images to expire before the tape can be reused.