The PREFIX controls what is written on the internal label as a dataset
name.

>From the 'help def devclass' output:

PREFIX
     Specifies the high level qualifier of the data set name that the
server
     writes into the sequential access media labels. For each
sequential
     access volume assigned to this device class, the server uses this
     prefix to create the data set name. This parameter is optional.
The
     default value is ADSM. The maximum length of this prefix is 8
more...   (<ENTER> to continue, 'C' to cancel)

     characters.

     If you have already established a media label naming convention
that
     supports your current management system, use a volume prefix that
     conforms to your naming conventions.

     Values specified for this parameter must meet the following
conditions:
        o The value is to be made up of qualifiers, which can contain
up to
          8 characters (including periods). For example, the following
value
          would be acceptable:

               AB.CD2.E

        o The qualifiers must be separated by a single period.
        o The first letter of each qualifier must be alphabetical or
          national (@,#,$), followed by alphabetical, national, hyphen,
or
          numeric characters.

     An example of a tape volume data set name using the default prefix
is
     ADSM.BFS.

>>> jamesez AT UMICH DOT EDU 02/14/06 7:03 AM >>>
Hi there,

We have the venerable IBM 3584, and I created a devclass "dbtape" with
a
prefix of "TDB".  I then printed a set of barcodes TDB001L2 ...
TDB015L2.
Checked in the tapes as scratch, labels=b, etc.  q libvol shows them.

When I went to backup db devc=dbtape, it picked a scratch tape with
a different prefix.

Does the PREFIX option actually do anything on an LTO library?

What I want is to use the PREFIX attribute to control which tapes can
be
used for a database backup, rather than maintaining a file of
appropriate
volume labels.

TIA,

--Jim