Database backup method
First Claim
1. In a distributed data base system having a central computer, a central computer main memory, a central computer mass memory, and a plurality of peripheral data base memories, a method of generating a backup copy of the contents of each of the peripheral data base memories in the central computer mass memory, comprising the steps ofsetting indications of modifications to the stored contents of a peripheral memory as modifications are made,executing a plurality of update passes on each of the peripheral memories, wherein each pass except the last pass includesallowing update modifications to occur to the peripheral memory being backed-up at a given time during execution of the pass,sequentially examining the modification indications and transmitting indicated modifications of the peripheral memory being backed-up at a given time from the peripheral memory to the mass memory,removing indications of modifications as the modifications are transmitted to the mass memory,executing a last update pass on each of the peripheral memories, wherein the last pass includesinhibiting update modifications to the peripheral memory being updated at a given time, andtransmitting all modifications to the peripheral memory being backed-up indicated to be present at the beginning of the last pass to the mass memory.
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Accused Products
Abstract
A method of generating a backup copy of a database system. Modifications made to the database since the generation of a prior backup copy are summarized in a bit map on a page basis. When the next backup copy is made, only modified pages are transmitted and merged with the prior copy. Plural backup passes are made. New modifications are allowed to occur to the database on all but the last pass. Any database modification made at an address that has already been examined during a pass is backed-up during the next pass. Modifications are locked out at the beginning of the last pass to allow the final generation of a consistent and complete backup copy.
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Citations
10 Claims
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1. In a distributed data base system having a central computer, a central computer main memory, a central computer mass memory, and a plurality of peripheral data base memories, a method of generating a backup copy of the contents of each of the peripheral data base memories in the central computer mass memory, comprising the steps of
setting indications of modifications to the stored contents of a peripheral memory as modifications are made, executing a plurality of update passes on each of the peripheral memories, wherein each pass except the last pass includes allowing update modifications to occur to the peripheral memory being backed-up at a given time during execution of the pass, sequentially examining the modification indications and transmitting indicated modifications of the peripheral memory being backed-up at a given time from the peripheral memory to the mass memory, removing indications of modifications as the modifications are transmitted to the mass memory, executing a last update pass on each of the peripheral memories, wherein the last pass includes inhibiting update modifications to the peripheral memory being updated at a given time, and transmitting all modifications to the peripheral memory being backed-up indicated to be present at the beginning of the last pass to the mass memory.
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5. In a distributed data base system having a central computer, a central computer main memory, a central computer mass memory, and a plurality of peripheral data base memories, a method of generating a backup copy of each of the peripheral data base memories in the central computer mass memory, comprising the steps of
A. maintaining a record of modification indications for each of the peripheral data base memories in the respective peripheral data base memory as information is modified in the peripheral memories, B. in response to a request by the central computer, sequentially locating any indications in the record and transmitting the associated modifications from a first one of the peripheral memories to the central computer and thence to the mass memory while allowing additional modifications to occur in all of the peripheral memories, C. clearing a modification indication in the record as each associated modification is transmitted to the central computer, D. repeating steps B and C for each of the remaining peripheral memories, E. at the completion of step D, repeating steps B, C and D zero, one or more times, F. at the completion of step E, inhibiting modifications to the first peripheral memory, G. at the completion of step F, sequentially locating any indication in the record and transmitting associated modifications in the first peripheral memory to the central computer and thence to the mass memory, H. clearing a modification indication in the record as each associated modification is transmitted to the central computer, and I. repeating steps F, G and H for each of the remaining peripheral memories.
Specification