The image shows operations between the application, the master database, the transaction log buffer, log files on disk, the subscriber database, a second transaction log buffer, and additional log files on disk.
The return receipt replication cycle is:
Commit transaction and block thread. (Application to master database)
Write update records to log. (Master to transaction log buffer)
Flush batch of update records to disk. (Transaction log buffer to log files on disk)
Send batch of update records to subscriber. (Transaction log buffer to subscriber database)
Acknowledge receipt of batch. (Subscriber sends to master.)
Unblock thread. (Master to application)
Write each received update record to log. (Subscriber to second transaction log buffer)
In a separate thread, flush batch of updates to disk. (Transaction log buffer to second set of log files on disk)
End of description.