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Database Administrator's Guide

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DELAYED_DURABILITY

DELAYED_DURABILITY <N>

DELAYED_DURABILITY <N> (default 0) controls whether or not to use the modified log syncing strategy:

  • When DELAYED_DURABILITY is set to 0 the new strategy is not in use.
  • When DELAYED_DURABILITY is set to a positive value, <N>, the new strategy is in use and the log sync is guaranteed to occur within <N> seconds. A setting of 1 second is recommended because it results in a good performance gain (higher values offer very little additional benefit). The following configuration options are set as shown below:

    SUPPRESS_LOG_FLUSH

    YES

    (no idle flush of transaction files)

    SUPPRESS_LOG_SYNC

    YES

     

    IDLE_TRANFLUSH

    -1

     

    COMMIT_DELAY

    -1

    (no commit delay)

    FORCE_LOGIDX

    ON

    (all transaction indices use ctLOGIDX)

    COMPATIBILITY LOG_WRITETHRU

    Disabled

     

Note: If the configuration file has one or more of these configuration entries set inconsistently after the DELAYED_DURABILITY entry, the server logs a message to CTSTATUS.FCS and continues to start, disabling any incompatible options after processing the configuration file.


Warning

When DELAYED_DURABILITY is enabled, recently committed transactions could be lost if FairCom DB Server terminates abnormally. For automatic recovery to succeed after FairCom DB Server terminates abnormally, either of the following must be done

  1. The application must write a restore point to the log (using the ctflush utility or calling ctQUIET() with mode of ctQTlog_restorepoint) so that a restore point exists prior to the time the server terminated abnormally. In this case, automatic recovery recovers to that restore point.

    or

  2. ctsrvr.cfg must contain the option RECOVER_TO_RESTORE_POINT NO, indicating that no restore point is needed. In this case, automatic recovery recovers to the last data that was written to the log on disk.

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