This topic describes how to view the data replication mode between a primary ApsaraDB RDS for SQL Server instance and its secondary ApsaraDB RDS for SQL Server instance.

Limits

  • The RDS instance runs RDS High-availability Edition or Cluster Edition. For more information, see High-availability Edition and Cluster Edition.
  • You cannot change the data replication mode of the RDS instance.

Data replication modes

  • Synchronous mode

    After an update that is initialized by your application is complete on a primary RDS instance, the log is synchronized to the secondary RDS instance. After the secondary RDS instance receives the log, the update transaction is considered committed. Your database system does not need to wait for the log to be replayed.

    If a secondary RDS instance is unavailable or the communication between a primary RDS instance and a secondary RDS instance is abnormal, the synchronous mode degrades to the asynchronous mode.

  • Asynchronous mode

    After an add, delete, or modify operation originated from an application is complete on a primary RDS instance, the primary RDS instance immediately responds to the application. At the same time, the primary RDS instance asynchronously replicates the added, deleted, or modified data to the secondary RDS instance of the primary RDS instance. In asynchronous mode, the workloads on the primary RDS instance run as expected even if the secondary RDS instance is unavailable. However, if the primary RDS instance is unavailable, errors may occur due to data inconsistencies between the primary RDS instance and the secondary RDS instance.

View the data replication mode

  1. Access RDS Instances, select a region at the top, and then click the ID of the target RDS instance.
  2. In the left-side navigation pane, click Service Availability to view the data replication mode of the RDS instance. 1