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Double Write/Single Check Output Method

IP.com Disclosure Number: IPCOM000079211D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Freiman, CV: AUTHOR

Abstract

There is described herein a method for effecting a double write/single check on output in any situation, wherein a read-back check is employed after a writing out from main store to an I/O unit.

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This is the abbreviated version, containing approximately 88% of the total text.

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Double Write/Single Check Output Method

There is described herein a method for effecting a double write/single check on output in any situation, wherein a read-back check is employed after a writing out from main store to an I/O unit.

As an example of a situation wherein such read-back check is employed, there is considered the case of a fixed-head-file (FHF). Thus, when a writing to an FHF is effected, it is common to use the first free sector therein which is available. The record is then held in main store for an additional rotation While, concurrently, a longitudinal residue check is performed to ascertain whether the written out information has been recorded without error. However, maintaining the record in main store is expensive in terms of system resources.

This method overcomes the costly problem of maintaining the record in main store. It comprises the following steps:
1) Each write which is free to use the first available storage

space is performed twice, using the first pair of available

spaces. (If the second write cannot be completed within a !

revolution, a read-back check is employed.)
2) At the completion of the second write, main store is freed.
3) The first of the two written-out records is then checked.
4) If the first checked record is correct, then the FHF storage

space holding the second written-out record is freed.
5) However, if the first written-out record is ascertained to be

in error, then the space containing this first record is

free...