HELP! * GREY=local LOCAL HTML version of Foils prepared July 6,1995

Foil 28 Example of failure due to lack of concurrency control

From Explicit Examples in Parallel Relational Databases CPS600 Spring Semester -- April 1995. by Gang Cheng Marek Podgorny (Geoffrey Fox) * See also color IMAGE
Time Steps:
  • Step 1: Node 1 reads block 1 from disk and stores in Node 1 memory cache, Node 2 reads block 1 from disk and stores in Node 2 memory cache
  • Step 2: Node 1 writes information to block 1, Node 2 writes information to block 1
  • Step 3: Node 1 writes block 1 to disk
  • Step 4: Node 3 reads block 1 from disk and stores in Node 3 memory cache
In this situation, Node 1 and 3 have the same information in each memory cache, but Node 2 has an inconsistent cache.

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