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Compaction/Decompaction for Storage Subsystem Save/Restore Operations

IP.com Disclosure Number: IPCOM000046725D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Ouchi, NK: AUTHOR

Abstract

This invention relates to a DASD storage subsystem shared among multiple accessing CPUs. More particularly, upon a CPU applying a READ FULL TRACK CCW to the storage subsystem, the subsystem response is to compress data read from a designated DASD track for transmission to said CPU. Also, the storage subsystem, responsive to a WRITE FULL TRACK DECOMPACT CCW, will expand data from the CPU for writing onto the DASD. These coordinate CCWs have utility in a storage subsystem SAVE/ RESTORE operation. SAVE is a data processing operation that reads full tracks of a data set for storage onto another storage medium. The "Saved" data is kept as backup in case of failure of the primary or original data. The SAVE operation is a frequent operation occurring daily for critical data sets.

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Compaction/Decompaction for Storage Subsystem Save/Restore Operations

This invention relates to a DASD storage subsystem shared among multiple accessing CPUs. More particularly, upon a CPU applying a READ FULL TRACK CCW to the storage subsystem, the subsystem response is to compress data read from a designated DASD track for transmission to said CPU. Also, the storage subsystem, responsive to a WRITE FULL TRACK DECOMPACT CCW, will expand data from the CPU for writing onto the DASD. These coordinate CCWs have utility in a storage subsystem SAVE/ RESTORE operation. SAVE is a data processing operation that reads full tracks of a data set for storage onto another storage medium. The "Saved" data is kept as backup in case of failure of the primary or original data. The SAVE operation is a frequent operation occurring daily for critical data sets. In contrast, the RESTORE operation is its complement in which full tracks of data are written onto the DASD. It is well appreciated that compaction can reduce channel occupancy, the size of CPU storage buffers, and the amount of secondary storage. Relatedly, the effective data rate of the secondary storage device may also be increased by the compaction factor. Illustratively, for a compaction factor of at least two, channel utilization can be halved because of full track read or write operations, the CPU buffer size and the amount of secondary storage utilizing tape. A DASD storage subsystem responsive to a READ FULL TRACK CO...