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Serializability

What determines serial execution order?

The goal of concurrency control is to produce an interleaving of reads and writes so that the ordering of transactions implied by each conflict has no contradictions.

Serializable schedule

No cycle so no contradictions.

  • T1 < T2
  • T2 < T3
  • T2 < T4
  • T4 < T5

Possible serializations:

  • T1 < T2 < T3 < T4 < T5
  • T1 < T2 < T4 < T3 < T5
  • T1 < T2 < T4 < T5 < T3
  • ...

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