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Logical Data Set Size Algorithm

IP.com Disclosure Number: IPCOM000061492D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 20K

Publishing Venue

IBM

Related People

Bibolet, RP: AUTHOR [+4]

Abstract

This article is related to the next article in this bulletin. The described algorithm can enhance record selection when applied page data sets such as represented by the example below. Page data sets may reside on non-cached direct-access storage devices (DASDs), and which are formatted into contiguous records on the data set. A record is available if it is currently not allocated to any user of the data set. It may or may not contain previously written data. This algorithm locates a record at a user's request. After allocation to a user, he may read from or write to the record. When searching for available records in a data set, the algorithm attempts to limit the area of search to a "logical data set" which is a dynamically varying subset of the physically defined data set.

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Logical Data Set Size Algorithm

This article is related to the next article in this bulletin. The described algorithm can enhance record selection when applied page data sets such as represented by the example below. Page data sets may reside on non-cached direct-access storage devices (DASDs), and which are formatted into contiguous records on the data set. A record is available if it is currently not allocated to any user of the data set. It may or may not contain previously written data. This algorithm locates a record at a user's request. After allocation to a user, he may read from or write to the record. When searching for available records in a data set, the algorithm attempts to limit the area of search to a "logical data set" which is a dynamically varying subset of the physically defined data set. If an available record is not found within the logical data set, then the search proceeds through the remainder of the data set. The logical data set always begins at the beginning of the physical data set. Its size is proportional to data set utilization, that is, the more records in use on the data set, the larger the logical data set size. The search for an available record begins at a point within the physical data set known as the "cursor". The position of the cursor is taken as a "given" by this algorithm, that is, cursor movement and positioning are not determined by it. The algorithm consists of the following steps, taken each time records are to be se...