Soxmusthavefailedeitherbefore ustartsorafterucommits

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Unformatted text preview: is replicated at X, M and Z. T reads from X for A and C. Later, X fails. U reads from N for B. Later, N fails. W reads from M for B and from Z for A. If “Available Copies” policy is used for replication control, show what failure timelines must be met for each transaction to be able to commit. Solutions: All transactions must commit in the view they start. T must commit in a view which includes X (it reads A and C from X) and any available replica of B when it started. So X must have failed after T commits. N must have failed either before T starts or after it commits. N is in the view of U when it starts (it reads B from N), so N must be in the U’s view when it commits. N must have failed after U commits. Available copies of A and C at the start of U must remain the same at U’s commit. So, X must have fai...
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This note was uploaded on 02/07/2013 for the course CS 425 taught by Professor Hu during the Spring '08 term at University of Illinois, Urbana Champaign.

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