Administering APPC/IMS and LU 6.2 devices

This topic introduces APPC/IMS and describes how to administer APPC/IMS and LU 6.2 devices.

APPC/IMS overview
APPC/IMS, a part of IMS TM, lets you use the CPI Communications interface to build CPI application programs.
APPC/IMS flood control
The APPC/IMS flood control function helps prevent a sudden increase in the number of APPC/IMS transaction requests from exhausting IMS 31-bit private storage.
APPC/IMS application program interface
APPC/IMS has two distinct application program interfaces (APIs): the implicit and explicit interfaces. The same application program can use both APIs.
APPC/IMS application programs
APPC/IMS has three different types of application programs: standard, modified, and CPI Communications driven.
Establishing APPC/IMS
Before activating APPC/IMS, an IMS system definition is needed to specify 390 as the third parameter of the SYSTEM keyword for the IMSCTRL macro.
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.
Using MSC in an APPC/IMS environment
APPC/IMS uses the services of APPC/MVS™ and MSC to provide the communication interface for an MSC configuration.
Recovering APPC transactions in an MSC environment
The recoverability of an IMS LU 6.2 transaction depends on whether the message is recoverable, irrecoverable, discardable, or nondiscardable, and when an error occurs.
Transaction retry characteristics
IMS retries certain abend conditions.
Qualifying network LU names
You can use the same name for LUs on different systems by adding the network identifier. This eliminates the need to have unique names for every LU on every system in your complex. You can use the network-qualified LU name as the name of the partner LU to allocate remote LU 6.2 conversations and sessions.
Managing multiple LUs for a single IMS system
An IMS system can be represented on a network by more than one LU name. If more than one LU name exists for a single IMS system, you might need to specify which LU should process asynchronous outbound messages.
Reassigning an LU to another IMS system
You can reassign an LU from one IMS system to another by using MVS commands.
DFSAPPC system service
DFSAPPC is an IMS system service for exchanging messages between LU 6.2 application programs (LU 6.2 to LU 6.2), and between LU 6.2 application programs and IMS-managed LTERMs. Message delivery is asynchronous; messages are held on the IMS message queue until they are delivered.
APPC transaction security
The security options for APPC/IMS and LU 6.2 application programs are quite extensive. The partner systems can range from a single-user terminal or workstation to a multi-user system. All systems can have their own complex security environment. Security for IMS can be simple or complex.

Parent topic: CPI Communications and APPC/IMS