ApsaraDB RDS for SQL Server replicates data between a primary instance and a secondary instance using either synchronous or asynchronous mode. The mode is set automatically based on your instance configuration and cannot be changed manually.
Prerequisites
Before you begin, ensure that you have:
An RDS instance running RDS High-availability Edition or RDS Cluster Edition
Data replication modes
Synchronous mode
In synchronous mode, a transaction on the primary instance is committed after the secondary instance confirms log receipt. The log does not need to be replayed before the commit is acknowledged.
If the secondary instance becomes unavailable or communication between the primary and secondary is interrupted, synchronous mode automatically falls back to asynchronous mode.
Asynchronous mode
In asynchronous mode, the primary instance responds to the application immediately after an operation completes, then replicates data to the secondary in the background. Workloads on the primary continue running even if the secondary is unavailable.
If the primary instance fails before replication completes, the secondary may not have the latest data, which can cause data inconsistencies.
View the replication mode
Go to the Instances page. In the top navigation bar, select the region where your RDS instance resides. Find the instance and click its ID.
In the left-side navigation pane, click Service Availability