Scheduling Characteristics of the APPC/MVS Transaction Scheduler

When an inbound APPC/MVS transaction program is scheduled by the APPC/MVS transaction scheduler, it is distinguished from other MVS work as follows:

Initialization

In response to an inbound allocate request from its partner, a transaction program is initiated through a program controlled interface, namely the allocate callable service. If the allocate service follows the LU 6.2 protocol, it can be issued from a program on the local MVS and from a program in a different operating system or even in a different network. For information about the Allocate call and other callable services used in APPC, see z/OS MVS Programming: Writing Transaction Programs for APPC/MVS.

Definition

Each inbound APPC/MVS transaction program is defined by a TP profile that is created by the installation and stored in a VSAM key sequenced data set. The TP profile contains scheduling parameters and a subset of JCL to define resource requirements. For information about TP profiles, see Controlling the Execution of Transaction Programs. For information about the subset of JCL to use, see Specific Scheduler JCL Information for TP Profiles

Output

APPC/MVS-scheduled TPs can use the same JES SYSOUT functions available to other MVS applications, with the exception that SYSOUT data sets allocated by TPs are treated as spin data sets. To guarantee that spin data sets are processed before initiator cleanup, IBM® recommends that all SYSOUT specifications, for both standard and multi-trans TPs, include the FREE=CLOSE parameter. For more information about SYSOUT processing, see Specific Scheduler JCL Information for TP Profiles.

If the installation changes the default subsystem for APPC work with the SUBSYS parameter in an ASCHPMxx parmlib member, then JES services may be unavailable to APPC/MVS-scheduled TPs.

Performance

Transaction initiators are managed based on response time goals set for classes. Classes are defined in an ASCHPMxx parmlib member, and a TP is assigned to a class in its TP profile. More information about classes appears later in this chapter and in Defining Scheduling Characteristics with ASCHPMxx. Information about how to set a response time goal appears in Defining Classes and Response Time Goals.

For information about APPC performance, see APPC/MVS Measurement and Tuning.

Management

System management facilities (SMF) provides records to support transaction programs running on an z/OS system, and the Resource Measurement Facility (RMF) reports on this work. For more information about the support SMF provides, see Using SMF to Audit APPC Work.

Security

Authority to use a transaction program can be controlled by a security product. Transaction programs can be made available as a public resource, or can be limited to particular users or groups of users. For more information, see Setting up Network Security.

Problem Determination

Transaction program processing is logged differently from work scheduled by a job entry subsystem. Runtime execution messages are written to a TP message log, the name of which is specified in the TP profile. For more information about logging, see Logging Transaction Program Processing.

When APPC/MVS finds errors during processing of inbound requests, APPC/MVS can send error log information to a partner system or program. Error log information describes errors that APPC/MVS finds when it tries to schedule a TP, such as problems with logical unit (LU) definitions or problems with processing allocate requests. Alternate transaction schedulers can also send error log information when processing their inbound requests.

For information about how an alternate scheduler can send error log information and the format of the variable that is used to send that information, see the description of the Cleanup_TP service in z/OS MVS System Messages, Vol 3 (ASB-BPX).