Browse Prior Art Database

Message Facility for Scoping Environmental Changes to a Job

IP.com Disclosure Number: IPCOM000052759D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 3 page(s) / 70K

Publishing Venue

IBM

Related People

Demers, RA: AUTHOR [+2]

Abstract

A facility is provided for scheduling cleanup or backout functions when programs terminate unexpectedly in a computer system. Many programs are invoked to provide a global change to the environment in which a job executes. For example, a ""file override'' command changes a file or the attributes of a file to be processed by subsequent programs of the job. The duration of these environmental changes can be limited by scoping them to the existence of a program invocation, a job step, or a job. Similarly, a program invocation can create temporary objects or conditions that must be destroyed or backed out at its own termination.

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Message Facility for Scoping Environmental Changes to a Job

A facility is provided for scheduling cleanup or backout functions when programs terminate unexpectedly in a computer system. Many programs are invoked to provide a global change to the environment in which a job executes. For example, a ""file override'' command changes a file or the attributes of a file to be processed by subsequent programs of the job. The duration of these environmental changes can be limited by scoping them to the existence of a program invocation, a job step, or a job. Similarly, a program invocation can create temporary objects or conditions that must be destroyed or backed out at its own termination.

However, a program invoked in a stack of programs cannot depend on being given control when the request or job for which it was invoked is terminated. Such terminations can occur for the following reasons:

User or system operator cancellation of the job or request.

Invocations destroyed due to exception processing.

Process termination due to job being rerouted or transferred to a different processing subsystem.

The present mechanism enables execution of cleanup and backout operations even under unusual terminations.

This mechanism depends upon the existence of a Job Message Queue in which a logical message queue exists for each program invocation.

Dashed lines indicate the associate of a program invocation to a program message queue.

This mechanism also assumes or depends upon the existence of an Invocation Reference Facility through which a program can be scheduled for execution at the termination of a particular existing program invocation.

Scope messages can be sent to a program message queue or to the external message queue of the job. All scope messages have the same format: ##

Scope messages can be sent by a program to its program message queue to request either program invocation scoping or invocation-level scoping. The Message Handler component of the system enqueues the Scope Message on the program message queue and issues a Trace Invocation instruction to schedule an event handler when the program terminates. When the event handler is invoked at the termination of the program, it processes each Scope message on the program message queue.

For program invocation Scope messages, the program identified by a system pointer in the message is invoked and passed a copy of the variable data area of the mes...