TPX needs its own Structure. A TPX Control Facility structure name may not be the same as the VTAM CF structure name. In fact the two should be unique.
A TPX Coupling Facility structure name is a combination of:
Coupling structure name prefix: ABCDEFGH (Max eight characters) and VTAM Generic Resource name: GRSCNAME (Max eight characters) (See SMRT option 12)
From the above sample, the TPX CF structure name would be ABCDEFGGRSCNAME.
Coupling structure name prefix - Provides the first eight bytes of the coupling facility structure name and also indicates to TPX that the coupling facility and Generic Resource facility will be used. This field must be eight non-blank characters following the coupling facility structure conventions. The last character cannot be an underscore character.
VTAM Generic Resource name - Provides the name of the VTAM Generic Resource of which this TPX will be a member as well as the last eight bytes of the coupling facility structure name. If the Coupling structure prefix is defined, then this field must also be defined. This field must be a valid VTAM resource name.
The TPX CF string name can be up to 16 characters long. This must be defined to the system as a separate CF structure in addition to the VTAM CF structure.
ISTGENERIC is not a "prefix" but rather the full name of the coupling facility string that is used for IBM products. Since TPX is not an IBM product, it should not share the IBM ISTGENERIC string. The full name for the TPX coupling facility string would be an 8 character prefix and the 1 to 8 character generic resource name that is to be used for that TPX Generic Resource.