What is the process to undo a DASD Cache expansion and regain the volumes used?
Release: Component: VTAPE
As for how hard it is to get cache back, it depends. Vtape has four types of data sets that could end up in the cache:
1) Virtual Volume data sets -- prefix.VVE.Vvolser.MM.CACHE. 2) Virtual Device work data sets -- prefix.VVE.Vdevnum.Ssystem. 3) Data queue data set -- prefix.VVE.VDATAQ... 4) If the Tasklib parameter is set to automatic, a special loadlib -- prefix.Ddate.Ttime.LIBn.
The Virtual Volume data sets can be moved with any standard data mover like ADRDSSU, FDR, CA Disk, etc. Vtape does not have any location specific information concerning these data sets in its control data sets. When one of these data sets is needed, Vtape requests its location from the catalog. The only time these data sets are enqueued is when there is a mount being serviced for the Virtual VOLSER whose data is in one of these data sets. If the only data sets on the cache DASD volumes you want to remove from cache are these data sets, you just update SMS to put the required volumes into DISNEW status and then run your data mover of choice to copy these data sets to other volumes. When the volumes are empty, remove them from the SMS storage group and repurpose them. The Virtual Device work data sets are enqueued while Vtape is active. The only way you can move these guys is with something like IBMS TDMF which will move them and then dynamically switch the volumes otherwise you have to stop Vtape. Once Vtape is stopped, you do not have to copy them. They are just work data sets with nothing permanent in them, so just delete them. When Vtape is restarted, it will check the catalog for them, find they do not exist and dynamically define a new one. If you update your ACS routines to send these guys to work packs or system packs, then you will not have to worry about moving them or deleting them and letting Vtape define them again. There is one of these for each Virtual Device so corralling them onto one DASD volumes is not a good idea. The VDATAQ data set is used to hold work in progress across stops and starts or IPLs. If the work is not completely, it will be restarted where it left off. This data set is also enqueue while Vtape is active and cannot be moved unless you use something like IBM's TDMF. Also, like the Virtual Device data sets, if you stop Vtape and delete the VDATAQ data sets, Vtape will just define a new one when restarted. If you add code to your ACS routines to send this guy to a work pack or a system pack, it might make your life easier when performing DASD evolutions in the future.