Initializing and changing LU 6.2 descriptors

LU 6.2 descriptors allow the system programmer to specify an LTERM that associates an output destination with an LU 6.2 application program. This allows the system programmer to change the application program's destination using alternate PCBs to LU 6.2 application programs, without requiring any application program coding changes.

LU 6.2 descriptors are optional, but they are required if you want to dynamically create queue control blocks and define processing options.

The application program uses an LTERM name as a symbolic destination; only the system programmer needs to be aware of the actual term associated with this name.

The LU 6.2 descriptor entry contains:

  • APPC/MVS™ side information entry name; this parameter can be omitted
  • APPC conversation type (BASIC or MAPPED)
  • APPC Sync_Level options (NONE, CONFIRM)
  • LTERM name
  • LU name of the destination of the LU 6.2 application program (overrides side information); this can be a network-qualified LU name up to 17 bytes in length
  • The name of the local LU that IMS uses to allocate the outbound conversation, specified in the OUTBND parameter
  • TP name to be scheduled (overrides side information)
  • VTAM® mode table entry to be used (overrides side information)
Here's an example of an LU 6.2 descriptor: 
U L62TERM1 LUNAME=L62IMS1 TPNAME=CPICTRN1 MODE=L62MDE02
U L62TERM1 SYNCLEVEL=N OUTBND=MYLU02

Do not code a parameter and leave it blank (such as SIDE=␢), or an error message is issued. Instead, omit the parameter completely.

These LU 6.2 descriptor LTERMs are only for output and are never used by IMS as an LTERM name associated with an input message. DFSAPPC is an IMS-reserved name for the message switch facility.

The LU 6.2 descriptors are built as specified in IMS PROCLIB member DFS62DTx during IMS initialization. They can be added, deleted, or changed without restarting IMS. You can specify any number of descriptors. If an error occurs, the z/OS® system console and the IMS JOBLIB record the error messages. IMS initialization continues regardless of any errors during descriptor initialization.

To add descriptors while IMS is running, you must first define the LU 6.2 descriptors in PROCLIB member DFS62DTx. Load the LU 6.2 descriptor from the IMS PROCLIB using the /START DESC command. To delete descriptors, use the /DELETE DESC command. To change descriptors, use the /CHANGE DESC command.

Related reading: For more information on coding these parameters, see IMS Version 15.2 System Definition.