To clarify the meaning and usage of the replication pause time setting as well as what this setting means and the possible implications.
During replication, certain environment variables such as network and disk speeds may adversely affect replication, causing the VPG to enter a 'Bitmap Sync' in order to synchronize the protection and recovery sites. During the Bitmap Sync, checkpoints are not generated and there is a gap in the journal history until the VPG re-enters protecting status. Once protecting, the journal history will begin to build again.
During the Bitmap Sync, the journal at the recovery site will continue to commit data to the recovery disks as they move out from the journal. If the amount of time the VPG is in a bitmap sync is GREATER than the amount of history currently in the journal, there is a risk of having no checkpoints available for recovery operations since all checkpoints will be committed.
The "Replication Pause Time" feature in the VPG settings will add a delay in such cases once there are 200 or fewer checkpoints present in the journal. If configured, Replication Pause Time can pause the sync for the configured period when the history is about to be cleared. During this period, the user may initiate a failover test to a specific checkpoint followed by a clone to the validated failover test checkpoint for the VPG so as to retain a historic copy. When the Replication Pause Time period expires, the system automatically resumes the Bitmap Sync, unless a clone or a recovery operation is still in progress. The user may also resume the Bitmap Sync manually within the GUI, by ending the pause early than configured in the VPG summary screen.
For example, if Replication Pause Time is set to 30 minutes, the user can trigger a clone or failover test within these 30 minutes. The 30 minutes timer will begin when there are 200 checkpoints or fewer left in the journal during a Bitmap Sync. Once the 30 minutes have expired, the system will begin committing data to the recovery disks again unless an aforementioned operation is in progress.
To enable or disable Replication Pause Time, set the Replication Pause Time value in the advanced site settings.
Zerto recommends configuring a replication pause time that aligns with your organization needs. This varies based on the above considerations. If a replication pause time is invoked automatically by the system, Zerto recommends that either the VPG is cloned to the last checkpoint or that a failover test is first performed to a specific checkpoint to ensure the VMs in the VPG are operating successfully and then a clone should be initiated to this failover test checkpoint.