Replication delay for "old" data

Replication delay identifies how frequently "old" data -- which includes inserts, updates, and store-and-forward data -- is sent from the one tier to the next-tier Historian. The replication delay applies only to queued replication.

You specify the delay using the OldDataSynchronizationDelay system parameter. For more information, see System Parameters.

This delay represents your intent, while the replication latency identifies the real time difference. If the latency period becomes longer than the replication delay, the system will not be able to maintain the expected replication.

If you set the OldDataSynchronizationDelay system parameter to 0 (zero), all changes detected in the lower-tier are immediately sent to the next-tier Historian(s), which may be very inefficient for certain applications.