This topic describes how to migrate an ApsaraDB RDS for SQL Server instance across zones in the same region. After the migration is complete, the attributes, configuration, and endpoints of the RDS instance remain unchanged. The time that is required to complete the migration is based on the amount of data to be migrated. The migration can take a few hours.

Prerequisites

  • Your RDS instance runs SQL Server 2008 R2 with local SSDs.
  • The region where your RDS instance resides consists of multiple zones. For more information about regions and zones, see Regions and zones.

Fees

You are not charged for the migration. This applies even if you migrate your RDS instance from one zone to multiple zones.

Impacts

  • During the migration, your database service may be unavailable for a short period of time. Make sure that your application is configured to automatically reconnect to your RDS instance.
  • The migration causes changes to the virtual IP addresses (VIPs) of your RDS instance. We recommend that you use an endpoint rather than an IP address of your RDS instance to connect your application to your RDS instance.
  • After the migration, you must immediately delete the cached DNS records from the database client. If the database client runs on a JVM, we recommend that you set the time-to-live (TTL) in the JVM configuration to 60 seconds or less. In this case, if the virtual IP address that is bound to the in-use endpoint of your RDS instance changes, your application can query the related DNS records again to obtain the new virtual IP address. Then, your application can connect to the new virtual IP address.
    Note The following TTL-setting methods are provided for reference:
    • Set the TTL for all JVM-based applications: Set the networkaddress.cache.ttl parameter in the $JAVA_HOME/jre/lib/security/java.security file to 60.
    • Set the TTL only for local applications: Specify the networkaddress.cache.ttl java.security.Security.setProperty("networkaddress.cache.ttl" , "60"); setting in the initialized code of the local applications. This must be completed before you call the InetAddress.getByName() function for the first time or before you establish a network connection.
  • If your RDS instance is associated with an DRDS instance, the VIP changes temporarily interrupt the connection between your RDS instance and the DRDS instance. You must manually configure the connection at the earliest opportunity. For more information, see Fix database shard connections.
  • If your RDS instance has an ongoing Data Transmission Service (DTS) task, you must restart the DTS task after the migration is complete.

Migration scenarios

Migration scenario Description
Migration from one zone to another zone The original zone where your RDS instance resides cannot ensure service performance due to issues such as heavy loads.
Migration from one zone to multiple zones You want to implement disaster recovery across data centers. After the migration is complete, your RDS instance and its secondary RDS instance reside in different zones.

The multi-zone deployment method delivers higher disaster recovery capabilities than the single-zone deployment method. If you select the single-zone deployment method, your database system can withstand server and rack failures. If you select the multi-zone deployment method, your database system can withstand data center failures.

Migration from multiple zones to one zone You want to use specific features that are supported only for the single-zone deployment method.

Procedure

  1. Visit the RDS instance list, select a region above, and click the target instance ID.
  2. In the upper-right corner of the Basic Information section, click Migrate Across Zones.
  3. In the dialog box that appears, specify the destination zone, vSwitch, and switching time. Then, click OK.

    After you click OK, ApsaraDB RDS starts to copy the data of your RDS instance to the destination zone. This does not interrupt the running of your RDS instance. After all the data is copied to the destination zone, your workloads are switched over to the destination zone at the specified switching time (Switch Now or Switch Within Maintenance Window).

    Note
    • During the switchover, a transient connection error of about 30 seconds occurs. Make sure that your application is configured to automatically reconnect to your RDS instance. Otherwise, you must manually reconnect your application to your RDS instance.
    • If the DNS records cached on the client are not immediately updated after the migration is complete, some of your workloads may be switched over to the destination zone 10 minutes later. This causes another transient connection error.

Related operations

Operation Description
Migrate an instance across zones Migrates an ApsaraDB RDS instance across zones in the same region.