Browse Prior Art Database

Maintaining Cached DASD

IP.com Disclosure Number: IPCOM000049819D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Nolta, AH: AUTHOR [+4]

Abstract

Direct-access storage devices (DASDs), such as disk storage apparatus, have their performance enhanced by the interposition of a cache between the using host and the DASD. For automatic or offline maintenance, the host first determines the data it will need during the maintenance period. This data is transferred to the cache and pinned to the cache. Then the DASD is varied offline for offline maintenance or accessed directly by the host for automatic maintenance. Upon completion of the maintenance period, the pinning is removed, restoring normal operations to the cached DASD. Since the cache can be employed for several DASDs, the other DASDs not being maintained operate in the normal mode. While one or more of the DASDs can be maintained automatically or offline.

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Maintaining Cached DASD

Direct-access storage devices (DASDs), such as disk storage apparatus, have their performance enhanced by the interposition of a cache between the using host and the DASD. For automatic or offline maintenance, the host first determines the data it will need during the maintenance period. This data is transferred to the cache and pinned to the cache. Then the DASD is varied offline for offline maintenance or accessed directly by the host for automatic maintenance. Upon completion of the maintenance period, the pinning is removed, restoring normal operations to the cached DASD. Since the cache can be employed for several DASDs, the other DASDs not being maintained operate in the normal mode. While one or more of the DASDs can be maintained automatically or offline.

Each DASD has a plurality of address modifiers. A first address modifier 00 enables the host to go directly to a DASD. Three other address modifiers 01, 10, and 11 enable access to the DASD via the cache. In addition to the other addresses each DASD is uniquely identified by a device address (not shown). Accordingly, for sn eight-DASD storage system, there will be eight device addresses; each device address will have a modifier address 00 through 11 (binary) for indicating the type of access. In an eight-DASD system, the address range is 00 to lF (hexadecimal).

From time to time, maintenance procedures will be employed for maintaining the DASD. The operator (not shown) activates t...