Thank you everyone for your replies.  I was worried that discarding the DR
copy pool data may delete data from my primary storage pool.  I guess it
does not, as help on delete volume says:

DISCARDdata
     Specifies whether files stored in the volume are deleted. This
     parameter is optional. The default value is NO. Possible values are:

     No
          Specifies that files stored in the volume are not deleted. If the
          volume contains any files, the volume is not deleted.

     Yes
          Specifies that all files stored in the volume are deleted. The
          server does not need to mount the volume for this type of
          deletion.

          If the volume being deleted is a primary storage pool volume, the
          server checks whether any copy storage pool has copies of files
          that are being deleted. When files stored in a primary storage
          pool volume are deleted, any copies of these files in copy storage
          pools are also deleted.

          When you delete a disk volume in a primary storage pool, the
          command also deletes any files that are cached copies (copies of
          files that have been migrated to the next storage pool).

In my case, as the DR tape is a copy of my primary storage pool, I guess it
should be OK to delete the tape.

Regards,

Ramesh