Browse Prior Art Database

Compacting Indexed Data

IP.com Disclosure Number: IPCOM000048072D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Tennison, RD: AUTHOR

Abstract

Indexed data, such as count key data (CKD), can be compacted for saving space on a direct access storage device (DASD). The compactor adds a count field K to the compacted CKD, which is then stored in a fixed length memory.

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Compacting Indexed Data

Indexed data, such as count key data (CKD), can be compacted for saving space on a direct access storage device (DASD). The compactor adds a count field K to the compacted CKD, which is then stored in a fixed length memory.

CKD is often used in DASDs. Such data is indexed in that it includes a count field for indicating the data length and a key field for identifying the records or data affixed to the count and key fields. The data is variable length.

The CKD to be compacted is read from DASD through the compactor into a buffer, creating the form of CCKD (compacted CKD). A separate count field CRL, compacted record length, is generated by the compactor and is stored in the buffer following the CCKD record. The generated pairs, CCKD plus CRL, are stored in fixed block storage areas for convenience of storage management. Padding of the fixed block versus management of record overflow is optional. Other control information, such as cylinder and track addresses, may be required, as well as some identifiable pair separator for use during decompaction.

When data is required by a user, it must first be decompacted. The first field to be decompacted is the count field of the CKD record which contains the Key Length and Data Length in fixed locations within the decompacted field. These two lengths are intercepted by the compactor to determine when the entire CKD record had been restored to its original form. The number of bytes used from the CCKD f...