The synchronize standby feature of the MultiPlatform resolves the unrecoverable transaction log gap in standby. This can happen under these circumstances.
Adhoc transaction log backups are taken in the primary, breaking the log chain between the primary and standby.
An ad-hoc full backup was taken with tail log backup that breaks the log chain.
One or more transaction log backup files are lost in standby before getting applied in standby.
The Sync feature, in summary, does the following:
Checks the current LSN number of the standby.
Take a differential backup of the primary database based on the LSN number on standby.
Transfer the differential backup to standby.
Restore the database backup on standby.
Delete unwanted transaction log backups that are present on standby.
Resume the automated update.
Click on Synchronize to start the process and press start to start the sync process.