Browse Prior Art Database

Duplex Pair - Pack Change Interrupt

IP.com Disclosure Number: IPCOM000100381D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 32K

Publishing Venue

IBM

Related People

Crockett, RN: AUTHOR [+6]

Abstract

A new instruction is disclosed which allows host software to identify the secondary device associated with the primary device of a duplex pair on command. A duplex pair consists of two DASD devices, primary and secondary, which are identically updated with each write operation. The duplex pair prevents the loss of access to critical data in the situation where the primary device of the duplex pair becomes inaccessible due to malfunction. Knowledge of the grouping of primary and secondary devices as duplex pairs is required by the host software to ensure proper host data management. The problem thus presented and herein solved is how to provide the host software with the ability to identify the member devices of a duplex pair.

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Duplex Pair - Pack Change Interrupt

       A new instruction is disclosed which allows host software
to identify the secondary device associated with the primary device
of a duplex pair on command.  A duplex pair consists of two DASD
devices, primary and secondary, which are identically updated with
each write operation.  The duplex pair prevents the loss of access to
critical data in the situation where the primary device of the duplex
pair becomes inaccessible due to malfunction.  Knowledge of the
grouping of primary and secondary devices as duplex pairs is required
by the host software to ensure proper host data management.  The
problem thus presented and herein solved is how to provide the host
software with the ability to identify the member devices of a duplex
pair.

      The aforementioned problem is solved by a new channel command
word which instructs a storage control, given a primary device, to
identify the secondary device in the duplex pair.  The instruction
causes the subsystem to issue a pack change interrupt from the other
address of the duplex pair.  The pack change interrupt includes
subsystem status, device status, and configuration information,
thereby identifying the secondary device.  A control block storing
the identities of duplex pair devices and their respective status can
thus be maintained by the host.