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Browse Prior Art Database

Buffer Search Technique

IP.com Disclosure Number: IPCOM000081799D
Original Publication Date: 1974-Aug-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Kinkade, D: AUTHOR [+2]

Abstract

In a part of IMS/VS it is necessary to search a buffer pool for a particular block of data. This can now be done by the described method which may be combined with many common buffer handling techniques.

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Buffer Search Technique

In a part of IMS/VS it is necessary to search a buffer pool for a particular block of data. This can now be done by the described method which may be combined with many common buffer handling techniques.

Each buffer is chained on two chains. The RR chain is ordered with the most recently referenced buffers first. The BN chain is ordered by an ascending data identifier (ID). In this case the ID is the block number of the block of data, but other ID's, such as record key, full disk address, relative byte address, or message sequence number could be used. Also, the BN chain could be ordered in descending rather than ascending order, but this would be desirable only if data references tended to occur in descending order. The method capitalizes on the application's tendency to refer either to a recently referenced ID, or to an ID which closely follows a recently referenced ID. This tendency is often encountered in buffer handling applications.

The method, as shown in the flow chart, starts with a search of up to K+1 buffers on the RR chain. The exact value of K is not critical. The value currently used is the number of buffers in the pool divided by eight, and the number of buffers is typically between ten and one hundred.

The second part oi the search proceeds along the BN chain. The important feature of the method is that the pointer J is set during the first part of the search, at the step marked A in the flow chart, to a better starting val...