Immediate Updating with Queued Updating as a Failover

Immediate updating with queued updating as a failover can be used when you expect the Publisher and Subscribers to be connected, but you do not want to lose the ability to make updates at the Subscriber if a system failure results in the loss of network connectivity. Immediate updating with queued updating as a failover allows you to use immediate updating and switch to queued updating when needed.

In this case, 2PC is used to propagate updates made at the Subscriber to the Publisher until you enable the queued updating failover. After the queued updating failover is enabled, transactions from the Subscriber are packaged into messages and sent to a queue. The transactions are recorded asynchronously and are applied to the Publisher when a connection is re-established.

You can invoke queued updating failover at any time, but after you do, you cannot failback to immediate updating until the Subscriber and Publisher (or Distributor and Publisher in the case of Message Queuing) are connected and the Queue Reader Agent has applied all pending messages in the queue to the Publisher. Queued updating is not invoked automatically because it may be easy to fix the problem that is preventing immediate updating (for example, hardware that is disconnected). You may not need or want to allocate resources to switch from queued updating back to immediate updating (which requires emptying the queue).

Pull subscriptions created using on-demand synchronization are added to Windows Synchronization Manager automatically. You can add pull subscriptions that are not using on-demand synchronization to Windows Synchronization Manager by opening the subscription properties, and then on the Synchronization tab, selecting Enable this subscription to be synchronized using the Windows Synchronization Manager.

To enable immediate updating with queued updating as a failover