The three modes of replication - synchronous, asynchronous, and synchronous override - work as follows:

• The synchronous mode waits until the Network Acknowledgment has been received from the secondary host before it completes the write to the application. Thus, the primary and the secondary have the same data.

• The asynchronous mode completes the application write after it has been written to the primary Replicator Log volume.

  If the primary site goes down, there may still be some writes that were not yet received at the secondary site. This mode has better performance but with a risk of some data loss.

• The synchronous override is a mode of replication that is synchronous as long as the network is available, but when the network becomes unavailable, the replication is continued in the asynchronous mode.