Allows you to access the subfields in the virtual tape system parameter
set by the Pre-ACS Installation Exit. The parameter is defined as
a 256-byte character string including one or more sets of 2-byte length
field followed by the value. The use of &MSPARM(n), where n is
the field number, indicates that indexing is requested. If &MSPARM
is specified without indexing, then the default is to access the first
field of the parameter (for example, &MSPARM1) result by default).
&MSPARM first field of the parameter (default)
&MSPARM(1) first field of the parameter
&MSPARM(4) fourth field of the parameter
The only accepted values for indexes are numbers from 1 - 71.