Ambiguous volume serial numbers

If several tapes with the same VSN are mounted concurrently in a computer center, the operator is asked via a user request to allocate the correct tape.

Device management guarantees that only one volume with a given VSN can be written at any one time. However, “SPECIAL” applications (INIT, VOLIN,...) may be running at the same time and may be using volumes with the same VSN. Device management has no way of protecting the user against mistakes by the operator; this means that a false tape with the specified VSN may be assigned by the operator after an INOP and that tape processing may be continued on a second volume.

Ambiguous VSNs may, for example, occur in a computer center which processes tapes belonging to different clients.