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Access control method for shared duplex direct access storage device and computer system therefor

  • US 5,202,887 A
  • Filed: 06/21/1990
  • Issued: 04/13/1993
  • Est. Priority Date: 06/21/1989
  • Status: Expired due to Term
First Claim
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1. A DASD access control method for use in a computer system comprising a plurality of processing units, a memory connected to said plurality of processing units and duplex direct access storage devices (hereinafter "DASD'"'"'s") accessible by said plurality of processing units, said duplex DASD'"'"'s comprising a first DASD for storing a plurality of data groups in addressable storage locations therein and a second DASD for storing a plurality of data groups in addressable storage locations therein, said first DASD and said second DASD including identical contents and one-to-one correspondence between the data groups stored in corresponding storage locations therein, wherein each one of said data groups of said first DASD and each corresponding one of said data groups of said second DASD form a data group set and are accessible as a logical unit by one of said plurality of processing units, said DASD access control method comprising the steps of:

  • (a) storing information in said memory device for identifying the invalidity of data groups in which an irrecoverable failure has occurred within said plurality of data groups stored in said first DASD and said second DASD;

    (b) judging whether one data group of a data group set stored in said first DASD and said second DASD and accessible by one of said plurality of processing units previously had an irrecoverable failure based on said stored information in said memory, when said one data group is accessed;

    (c) accessing said one data group of said data group set when said step (b) results in a determination that said one data group does not have an irrecoverable failure; and

    (d) stopping access to said one data group of said data group set when said step (b) results in a determination that said one data group has an irrecoverable failure.

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