Validation Tech. & Isolation Snapshot

Validation Tech. & Isolation Snapshot

1. Validation / Optimistic Concurrency Control

   • 1. READ
   • 2. VALIDATIION
     • No overlapping
       • If Overlapping
         • NO overlapping of Same Data
           • Finish(f) --> Start(S)
         • First Tr. must complete WRITE before Second Tr. enters into validation
           • WritePh(F) 'C' || 'E' Val.Ph(S)
             • Passes First Tr.
     • 3.WRITE

2. Snapshot Isolation

   • Shows Only Comm. Trans.
   • X
     • Dirty Problem
     • Avoid Non-repeatable read
   • Better than 2PL
     • No READ Lock
     • Only WRITE LOCK
   • Commercial Examples

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