The reuse delay parameter is used to define how long a tape will stay in a pending state. It is specified in days and can be applied individually to primary sequential and copy storage pools (in other words storage pools that handle tapes).
Why do we need this parameter? This parameter is used to ensure that if you had to restore your TSM Database to a previous days backup that the tapes will be in a consistent state with the TSM Database as at the point of the restore.
To Illustrate this, assume that the reuse delay parameter is set to 0 so that tapes become scratch tapes as soon as they are empty.
Monday
A TSM Database Backup is taken on Monday
Tape A1 currently has data for Node ZZ
Tuesday
The data for Node ZZ on tape A1 expires and because the reuse delay parameter is set to 0 tape A1 becomes a scratch tape
Tape A1 is now immediately used to backup node YY’s data
Wednesday
For some reason, you have to restore to the last TSM database backup which was taken on the Monday.
Because the database is now running as at Monday TSM believes that tape A1 holds the data for Node ZZ. A decision is made to restore data for Node ZZ which resides on A1 and TSM complains that the volume is corrupt because the data on the tape is not what TSM is expecting. In this case if the reuse delay parameter had been set to 2 days then tape A1 would not have been written on and the restore would work as expected.
How do I check for the tape status ?
Tapes that are empty but not yet available to be used as scratch tapes have a status of PENDING. To view pending tapes in TSM Studio open the Libraries and Volumes category and double click on the Volumes Dataview. As seen below check the “Status” column and look for tapes in a ‘PENDING” state.
To see when these tapes will become scratch tapes, check the Pending Date. This is the date that the tape went into a pending state. Add the Reuse Delay value to determine when the tape will go from a Pending State to becoming a scratch tape.
To find the Reuse Delay value check the Storage Pool that the Volume is in
Then goto the Storage Pools dataview locate the same Storage Pool name and check the Reuse Delay Column
How do I set the value for this parameter ?
I recommend that you set the value of this parameter to be equal with the number of days or TSM Database backups you keep.
To change the reuse delay parameter from the command line
Update STGPOOL STGPOOL_NAME REUSEDELAY=days
Where STGPOOL_NAME is the name of the storage pool and days is the value for the REUSEDELAY parameter
UPDATE STGPOOL TAPEPOOL REUSEDELAY=2 for 2 days
To change the reuse parameter from TSM Studio goto the Storage Pools Dataview, select the storage pool that you wish to modify, right click to bring up the context menu. Select Reuse Delay and choose the value (in days) you wish to set. Press Ok
Posted in: TSM Studio
