Automatic synchronization is accomplished by SQL Server. A snapshot is taken of the table schema and data of the published article, and that snapshot is written to files for transfer.
The synchronization process also creates a synchronization job and places it in the distribution database. When distributed, this job applies the files in the synchronization set to all subscription databases that are waiting for synchronization. The job to copy the table schema and data is transferred to the waiting subscribers as with any other replication job, via the distribution database. No operator intervention is required.
Automatic synchronization occurs on a scheduled basis. Since automatic synchronization of databases or even individual tables requires a fairly high amount of system overhead, a benefit of scheduling automatic synchronization for less frequent intervals is that it allows the synchronization snapshot to be scheduled for a period of low activity on the publication server.
When a scheduled initial synchronization time arrives, synchronization occurs only for those subscribers that have requested synchronization since the last sync event occurred (not for all subscribers to that publication). This minimizes the impact on the publication server.
Important A scheduled synchronization is based on the date and time at the distribution server (not the date and time at the subscription servers).