First, determine the name of your tape drive if not known.  Command is WRKDEVD T* usually.

Following is displayed:

None of these are tape drives.

If that does not give a tape device, then try wrkdevd *tap

Following is displayed:

Notice the Text will say something about the tape cartridge.

However, usually the tape drive name is T1, TAP01, TC, etc.

To initialize a tape, type INZTAP and press F4.  

The tape drive name is necessary, as is the Volume ID.  This should be a different name for each tape, i.e. mon1, tue1, wed1.  If you have 10 tapes, next week’s tapes would be mon2, tue2, etc. The system save tapes could be named syssv1, syssv2, etc.

Press enter.  The system will initialize the tape.