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  1. camunda BPM
  2. CAM-2120

Look into MSSQL & DB2 deadlocks

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    Details

    • Type: Task
    • Status: Closed
    • Priority: L3 - Default
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 7.2.0, 7.2.0-alpha1
    • Component/s: engine
    • Labels:
      None

      Description

      Problem:
      There are two classes of deadlocks:
      1) DB-Specific (Seen on MSSQL & DB2 only), caused by the DB locking scheme used by these databases as a default setting.
      2) Non-BD-Specific, Caused by conflicts resulting from Conflicting Concurrent Transactions (CCTs) inside the same Process Instance. (See CAM-1971)

      Class 1 deadlocks

      • may already occur for SELECT statements,
      • may already occur if data from different PIs is being selected / modified,
        => have high probability to occur.

      Class 2 deadlocks

      • need unfortunate interleaving of UPDATE / DELETE,
      • only occur if CCTs are executed inside the same PI,
        => have low probability to occur.

      Objectives:

      • We want to get a feel whether Class 1 Deadlocks can be resolved by enabling snapshot isolation in these databases and if true document this setting.

      AT:

      • Testcase for class 1 Problems is available and ca be run as part of CI build
      • If applicable (depending on results): Proper isolation level Settings for MSSQL & DB2 are mentioned in Docs (latest / 7.1 / 7.0)

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              Assignee:
              sebastian.menski Sebastian Menski
              Reporter:
              meyer Daniel Meyer
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                Updated:
                Resolved: