Script to label recycle volumes

Since NetWorker does that automatically what is the purpose? If desired pool would be different from pool in which tape currently is you could allow this at pool level (by allowing recycle from and to settings). But to answer your question, yes what you wish is also possible even you could do it through NW configuration without any scripting.

Ideally, i would like to run a batch job daily to check for expire volumes for a specific pool and re-label them to the same pool.

Would a nsr_label work? Or is there a better way/

This is for a virtual tape library. And drive space is limited. When we added the VTL, we didn't think about the repercussion on creating so many volumes. It's a problem now.

I see... relabeling this immediately you would free up some space physically on VTL. Yes, this is possible. Hopefully you know how to translate following into the script:
- list (all) volumes which are recycable (use mminfo for that)
- (re)label them (nsrjb)

You have two variations here with same end result; one where you would list all volumes and then relabel them based on their earlier pool assigment (requires parsing data from mmino query) or by doing query for each pool you have and then relabel it back to that pool based on list of volumes obtained by mminfo query.

There other approaches like deleting expired media and having them handled further by auto media management (certain risk present as always when dealing with auto media management) or simply by list all expired volume and having them labeled to scratch pool and recycled immediately. Thus they would take no space and would be available to be relabeled by NW in case you allow recycle to for scratch pool and recycle from for other production pools. I'm quite sure there are other approaches too.

What is nsr_label?

Check mminfo and nsrjb manual for details. mminfo has switch to report recycled volumes (volrecycle) and in nsrjb manual you will find example how to label tapes.

What syntax would I use to create this command to check for expired volumes and label them to the same pool?