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Spotlight on Oracle 10.4 - Release Notes

Transport Lag Alarm

Keep Transport Lag low so your Recovery Point Objective can be met. You want transport to be quick so the Standby has all the information it needs to become the Primary (with minimal data loss) should the Primary go down.

For more information on Recovery Point Objective (RPO), refer to the Oracle Database Help Center.


  • There will always be a Transport Lag when the Archiver is used. The Archiver waits for the Archive Log to fill on the Primary before it transports the log to the Standby. Via the Log Network Server changes on the Primary are transported to the Standby as they happen. If there is a bottleneck on the Log Network Server then the Redo Log Writer will write the overflow to the Redo Logs to be transferred to the Standby via the Archiver. A bottleneck on the Log Network Server could be caused by a slow Network connection, particularly if the Transport Method is Synchronous or Parallelsync.
  • In Oracle versions prior to 11.2 some configurations experience inconsistent or misleading data on the Transport Lag. This is documented as Oracle Knowledge Article [ID 1299000.1].

    An Example Scenario: Outstanding Logs are speedily applied. Therefore you would expect the Transport Lag to be low, but the Transport Lag is increasing. The Transport Lag data is misleading. Disable the Transport Lag Alarm and use the Outstanding Logs To Ship Alarm to check for bottlenecks.


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