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Method and apparatus for performing point in time backup operation in a computer system

  • US 5,857,208 A
  • Filed: 05/31/1996
  • Issued: 01/05/1999
  • Est. Priority Date: 05/31/1996
  • Status: Expired due to Term
First Claim
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1. In a data network including a first data processing system with a first host computer and a first data storage facility for processing application programs, including a second data processing system with a second host computer, a second data storage facility and a backup facility for providing a copy of the data in the second data storage facility on separate media, and including a communications link for interconnecting the first and second data processing systems, the second data processing system operating in a normal operating mode to mirror the first data storage facility by transferring data through the communications link and wherein each of the data storage facilities includes at least one disk storage device characterized by a plurality of tracks and by block data transfers having a one-track length, the improvement of a method for enabling the backup of the data in the network without interfering with the operation of the first data processing system, said method comprising the steps of:

  • (A) enabling from the second data processing system a backup operating mode by disabling transfers over the communications link and initiating a backup operation from the second data storage facility to the backup facility, the backup operation occurring in parallel with operations in the first data processing system(B) recording, in the first data processing system, each transfer to the first data storage facility during the backup operating mode produced the first data processing system,(C) converting, upon return from the backup operating mode to a normal operating mode, the recordings of each transfer into a list of changed tracks, and(D) copying the data from each changed track of the first storage facility identified by the list of changed tracks to each corresponding track in the second date storage facility.

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