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Notification of Subsystem Availability

IP.com Disclosure Number: IPCOM000050908D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Athwal, DS: AUTHOR [+2]

Abstract

This article describes a method for allowing connecting application address spaces to know when a data base management subsystem instance is available, comprising the steps of: (1) issuing an IDENTIFY request by the connecting application to the subsystem instance, with the IDENTIFY request including a NOTIFY message parameter; (2) if the subsystem instance is available, processing the IDENTIFY request; otherwise, (3) queueing the NOTIFY message and upon the subsystem instance becoming available, processing the queued NOTIFY message.

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Notification of Subsystem Availability

This article describes a method for allowing connecting application address spaces to know when a data base management subsystem instance is available, comprising the steps of: (1) issuing an IDENTIFY request by the connecting application to the subsystem instance, with the IDENTIFY request including a NOTIFY message parameter; (2) if the subsystem instance is available, processing the IDENTIFY request; otherwise, (3) queueing the NOTIFY message and upon the subsystem instance becoming available, processing the queued NOTIFY message.

When application subsystems, such as IMS/VS Version 1, execute only as JOBs (or started tasks), they are limited as to the services they can provide. In particular, they must depend on the MVS system operator to inform potential users of the subsystem that it is available or let the users use a POLLing mechanism to catch the subsystem while it is up.

Today, for example, IMS/VS Version 1 requires that its users come up after it has come up or that they have their own means of knowing when IMS/VS is available.

Herein we describe a data base management (DBM) subsystem (DBMS) that is a formal subsystem of MVS, and its users may be IMS/VS Version 1, CICS/VS, TSO users, or batch jobs. Since the DBM subsystem allows its users to come up before, during, or after the DBM subsystem instance is started, a means is required to inform such users of the availability of the subsystem services.

In order to provide a means to allow users (connectors) of the DBM subsystem to be notified when the subsystem comes up and is operational, a small part of the DBM subsystem establishes itself as a formal MVS subsystem at MVS IPL time and stays active for the life of the IPL. The remainder of the subsystem comes up/down at the installation's discretion via subsystem -START and -STOP commands.

At MVS IPL time, DBMS utilizes the MVS Subsystem Interface (SSI) and initializes the SSI linkage tables to support the broadcast functions which support listening for command entry, connection (IDENTIFY) to DBMS, and address space (End...