During a test recovery, recovery, or reprotect, SRM issues and operation internally referred to as syncOnce, to synchronize the data in the SRM protection group.
ActiveDR has no specific "synchronize" operation because it is inherently always synchronizing as fast as it can. The underlying goal of this operation is to ensure that before the test starts is that at least the point-in-time of the start of the test is replicated to the second site. Therefore, the SRA makes use of the property in ActiveDR replica links called recovery point to ensure it is in sync.
The recovery point indicates the last point-in-time of the entire pod that is available on the second array. This is calculated by using the lag property (which says how far behind the replication is) and subtracting it from the current time. So if the lag is 30 seconds and the current time is 08:00:00, the recovery point is 07:59:30. So if the replication were to fail at that moment, ActiveDR would be able to recover all data, snapshots, configurations, etc. from 07:59:30.
So when SRM issues a synchronization, the SRA uses the timestamp of that request as the target point-in-time. If the recovery point is not at that time or later, the SRA will tell SRM to wait and try again. Once the recovery point equals or surpasses the identified timestamp, the synchronization is deemed to be complete.