Generic resources requirements

Any VTAM® application program running on a VTAM APPN node that is connected to an MVS™ coupling facility structure identified by the STRGR start option can be known by a generic resource name. All VTAM nodes having access to the common generic resource coupling facility structure, along with the structure itself, make up a generic resources configuration.

A generic resources configuration must be part of a sysplex environment.
All VTAMs in a generic resource configuration must be connected to an MVS coupling facility in which the generic resource structure can be allocated. VTAM connects to the generic resource structure when it is defined in the active CFRM policy.
The generic resource coupling facility structure stores the data needed by VTAM to implement the generic resources function. This data includes mappings that show:
- For each generic resource name, a list that identifies the generic resource members currently using that name. This is called a generic resource mapping.
- For each LU in session with one or more generic resource members, the application program network name and the generic resource name for each generic resource member. This is called a partner LU mapping.
In defining generic resource structure in a CFRM policy, you specify the amount of coupling facility storage which should be allocated on behalf of this structure. For information about determining the amount of storage necessary, see Determining the size of the coupling facility structure.
VTAM Version 4 Release 2 or later is required for all VTAMs in a generic resources configuration, and all VTAMs must be defined as network nodes or end nodes. If an application program is both a generic resource and uses multinode persistent sessions, all VTAMs in the sysplex must be Version 4 Release 4 or later.
If you are using subplexing (that is you have specified the XCFGRPID start option), all resources that share a generic resource name must reside within the same subplex. That is, they must be running on VTAMs that have been started with the same value for the XCFGRPID start option. In addition, the generic resource coupling facility structure within each subplex must have a unique name. To ensure this, the structure name specified by the STRGR start option is suffixed with the 2-character XCFGRPID start option value. You must ensure that each of these subplex structure names is defined in the active CFRM policy. For example, if you have two subplexes within your sysplex, one with XCFGRPID=11 and one with XCFGRPID=02, and your STRGR option specifies the structure name ISTMYGR, you must ensure that the CFRM policy defines both an ISTMYGR11 and an ISTMYGR02 generic resource structure. You can display the fully suffixed generic resource structure name accessed on a VTAM node by issuing the D NET,ID=VTAM command.
If instances of a generic resource exist on an end node, CP-CP sessions must exist between the end node and its network node server.
If instances of a generic resource exist in the domain of multiple network nodes, CP-CP sessions should exist between each pair of network nodes to ensure correct session setup.
The OLU host of a session initiation to a generic resource must support name translation. The TRANSLAT start option must include USERVAR.
A network node server is required to provide generic resource resolution for resources on end nodes within the generic resource configuration. The recommended APPN generic resource configuration consists of a network node and served end nodes connected to the same generic resource structure with a backup network node connected to the same structure. But a backup network node server that is not connected to the same generic resource structure can be used. This requires that the end nodes allow broadcast searches, by coding ENBCAST=YES on the NETSRVR list. See the ENBCAST operand on the NETSRVR statement for the VTAMLST VBUILD TYPE=NETSRVR list in z/OS Communications Server: SNA Resource Definition Reference.
If the network node server currently in use by the end nodes resides outside the sysplex, session setups to generic resources residing on these end nodes can fail if the NETSRVR list is not defined correctly. Symptoms of the failure would be similar to the following, where TSOXX is a generic resource name:
```
  IST663I  CD DSRLST  REQUEST TO   CDRMX  FAILED, SENSE=087D0001
  IST664I  REAL  OLU=netid.luname       ALIAS DLU=netid.TSOXX
  IST889I  SID = EC7F2F218E97F0CF
  IST1705I  SORDER = ADJSSCP  FROM START OPTION
  IST1705I  SSCPORD = PRIORITY  FROM START OPTION
  IST894I ADJSSCPS TRIED,FAILURE SENSE,ADJSSCPS TRIED,FAIL SENSE
  IST895I    ISTAPNCP       08400007     CDRMA         087D0001
  IST895I    CDRMB          087D000A     CDRMX         087D000A
  IST314I  END
```
VTAM uses default settings to control generic resource resolution. To modify the default settings for all or specific generic resources you must define a generic resource preference table using GRPREF operands on the GRPREF statement for the VTAMLST VBUILD TYPE=GRPREFS statement. For more information see z/OS Communications Server: SNA Resource Definition Reference. In addition, see Initiating sessions using the generic resource name.