Browse Prior Art Database

Channel Dual Address Compare Mode

IP.com Disclosure Number: IPCOM000100388D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 36K

Publishing Venue

IBM

Related People

Cortney, J: AUTHOR [+3]

Abstract

A system adapter (SA), operating in two general modes, connects a channel to a cluster of parallel paths for accessing a set of direct access storage devices (DASDs). In the first mode, address-independent path selection is available because each path in the cluster connects to the full set of DASDs. In the second mode, address-dependent path selection is required because each path in the cluster connects only to a subset of the set. Each SA includes an address compare register for each path in the cluster together with a mode control register. The mode control register indicates the number of paths in the cluster and whether address-independent or address-dependent path selection is required. In address-independent path selection, only one address compare register is used, and selection is based on path availability.

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Channel Dual Address Compare Mode

       A system adapter (SA), operating in two general modes,
connects a channel to a cluster of parallel paths for accessing a set
of direct access storage devices (DASDs). In the first mode,
address-independent path selection is available because each path in
the cluster connects to the full set of DASDs.  In the second mode,
address-dependent path selection is required because each path in the
cluster connects only to a subset of the set.  Each SA includes an
address compare register for each path in the cluster together with a
mode control register.  The mode control register indicates the
number of paths in the cluster and whether address-independent or
address-dependent path selection is required.  In address-independent
path selection, only one address compare register is used, and
selection is based on path availability.  In address-dependent path
selection, path selection is based on the DASD addresses served by
the paths and each address compare register is used.

      The mode control register in the SA determines the number of
channel address compare registers needed in order to satisfy the
different subsystem configurations possible. The address compare
registers store the control unit portion of the subsystem address.
The mode control registers contain the configuration information
about the number of channel address compare registers and the number
of storage paths that are to be used.