Browse Prior Art Database

Shared Record Validity Checker Control Unit Extension

IP.com Disclosure Number: IPCOM000043977D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Robinson, JT: AUTHOR

Abstract

There are several systems in use (in particular, some airline control program systems) in which multiple processors are used to increase system throughput, and in which a database is shared among the processors by means of shared secondary memory control units, as shown by the diagram below. (Image Omitted) Currently, once a shared record is read into a processor's local buffer memory, the copy cannot be retained in the buffer after the record is unlocked since it is possible that the record could be modified by applications running on other processors (also, it is unacceptable to leave a record locked overly long, since this would prevent other applications from running).

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Shared Record Validity Checker Control Unit Extension

There are several systems in use (in particular, some airline control program systems) in which multiple processors are used to increase system throughput, and in which a database is shared among the processors by means of shared secondary memory control units, as shown by the diagram below.

(Image Omitted)

Currently, once a shared record is read into a processor's local buffer memory, the copy cannot be retained in the buffer after the record is unlocked since it is possible that the record could be modified by applications running on other processors (also, it is unacceptable to leave a record locked overly long, since this would prevent other applications from running). The following describes an extension to control units that allows control units to determine when copies of shared records are valid, where a valid record copy is defined as one that has not been modified by another processor since it was read. For the purposes of description, a simplified logical interface to a control unit will be assumed, as follows. READ(RID, PNUM, ADR): transfer the record described by RID from secondary memory to the primary memory of processor PNUM at address ADR. WRITE(RID, PNUM, ADR): transfer the record described by RID from primary memory of processor PNUM at address ADR to secondary memory. The following is a new control unit function that requires modification of existing processor buffer management software. FORGET(RID, PNUM): must be used by processor PNUM when the processor discards its copy of the record described by RID. A fun...