When NUMBTAPE is specified on the IEHINITT control statement the
current restriction is that the original volume serial must be all
numeric. This restriction will continue to apply, however, the modified
volume serial need not adhere to this restriction.
Note: Iincrementation of the numeric volume serial value
is performed based on the value of the originally specified volume
serial. For example, if a volume serial of 002000 is specified on
the INITT card and exit processing results in the volume serial being
modified to 050000, the next volume serial to be processed will be
002001, not 050001.