FAQ about migrating data from an ApsaraDB RDS for MySQL Enterprise Edition instance to a PolarDB-X 2.0 Standard Edition instance -

This topic provides answers to some frequently asked questions about migrating data from an ApsaraDB RDS for MySQL Enterprise Edition instance to a PolarDB-X 2.0 Standard Edition instance.

Does the destination PolarDB-X 2.0 Standard Edition instance need to use the same node specifications as source ApsaraDB RDS for the MySQL Enterprise Edition instance?
No, the destination instance does not need to use the same node specifications as the source instance. You can select node specifications for the destination PolarDB-X 2.0 Standard Edition instance based on your business requirements. We recommend that you select node specifications higher than or equal to those of the source ApsaraDB RDS for MySQL Enterprise Edition instance.
Do I need to purchase a PolarDB-X 2.0 Standard Edition instance before the migration?
No, you do not need to purchase a PolarDB-X 2.0 Standard Edition instance before the migration. During the migration, you can purchase and create a PolarDB-X 2.0 Standard Edition instance that includes the same data as the source ApsaraDB RDS for MySQL Enterprise Edition instance.
Does the migration interrupt the running of the source ApsaraDB RDS for MySQL Enterprise Edition instance?
No, the migration does not interrupt the running of the source ApsaraDB RDS for MySQL Enterprise Edition instance.
Does the source ApsaraDB RDS for MySQL Enterprise Edition instance experience performance degradation during the migration?
No, operations performed on the source ApsaraDB RDS for MySQL Enterprise Edition instance are not affected during the migration. However, data synchronization involves query operations, which may affect the query performance of the source instance.
Does the migration affect my business?
Yes, but only slightly. You do not need to worry about data loss or shut down your source instance during the migration. The only impact is that data writes may be halted for a while. The time depends on the configurations. If you select switchover without endpoints, data writes to the source ApsaraDB RDS for MySQL Enterprise Edition instance are halted during the business switchover, which may last about 10 minutes. If you select switchover with endpoints, the data writes are halted for only about 30 seconds, which is similar to the time required for a primary/secondary failover. In addition, seamless rollback is supported to meet rollback requirements in special cases.
What happens if I cancel the migration?
Canceling the migration has the following impacts:
- The data synchronization link from the source instance to the destination instance is disconnected. The source instance is no longer associated with the destination instance.
- The destination instance becomes readable and writable and is not automatically released. If you no longer require the destination instance, release the instance at your earliest opportunity to prevent additional costs.
Do I need to change the endpoint configuration of my application after I switch over my business to the destination PolarDB-X 2.0 Standard Edition instance?
You can select the Switch with Endpoints (Connection Changes Not Required) option when you perform the migration and the switchover. The system then automatically switches the endpoints of the source ApsaraDB RDS for MySQL Enterprise Edition instance and the destination PolarDB-X 2.0 Standard Edition instance during the switchover. In this case, the application can automatically connect to the destination instance without the need to modify any configurations after the switchover.
Why does the destination PolarDB-X 2.0 Standard Edition instance use a new endpoint after the migration is complete even if I select the Switch with Endpoints (Connection Changes Not Required) option?
Endpoints can be switched only if both the source ApsaraDB RDS for MySQL Enterprise Edition instance and the destination PolarDB-X 2.0 Standard Edition instance have the endpoints. By default, only the primary private endpoints are switched. If you want to switch other endpoints, create the endpoints before the switchover. For information about how to create an endpoint for the source ApsaraDB RDS for MySQL Enterprise Edition instance, see Apply for or release a public endpoint. For more information about how to create an endpoint for the destination PolarDB-X 2.0 Standard Edition instance, see Apply for or release a public endpoint.
Does the system switch the endpoints of read-only instances in the source ApsaraDB RDS for MySQL Enterprise Edition instance if I select the Switch with Endpoints (Connection Changes Not Required) option?
No, the system does not switch the endpoints of read-only instances in the source ApsaraDB RDS for MySQL Enterprise Edition instance even if you select the Switch with Endpoints (Connection Changes Not Required) option.
Why do I fail to connect to the destination PolarDB-X 2.0 Standard Edition instance after I switch over my business or fail to perform write operations on the destination instance after the connection to the destination instance is established?
After the endpoints are switched, the old endpoint information may remain in the Domain Name System (DNS) cache before the endpoint information expires. During this time, you may fail to connect to the PolarDB-X 2.0 Standard Edition instance, or the instance supports only read operations. To resolve the issue, we recommend that you refresh the DNS cache of your server.
Note
You can refresh DNS cache data based on the actual operating system and version of your server. The following example shows how to refresh DNS cache data in Alibaba Cloud Linux 2/3:
1. Check whether the systemd-resolved service is running. If the service is running, a status message similar to Active: active (running) is returned.
```
sudo systemctl status systemd-resolved
```
2. Refresh the DNS cache data of the systemd-resolved service.
```
sudo systemd-resolve --flush-caches
```
Why is the Complete Migration button not displayed for the PolarDB-X 2.0 Standard Edition instance in the PolarDB-X console after data is migrated and my business is switched over to the destination instance?
After you have completed the Complete Migration step, the button is no longer displayed, so as to prevent repeated operations.
Do I need to replicate the accounts and passwords of the source ApsaraDB RDS for MySQL Enterprise Edition instance to the destination PolarDB-X 2.0 Standard Edition instance after the migration?
No, you do not need to replicate the accounts and passwords of the source instance to the destination after the migration. After the migration, the destination PolarDB-X 2.0 Standard Edition instance contains the same accounts, passwords, databases, IP address whitelists, and required parameters settings as the source ApsaraDB RDS for MySQL Enterprise Edition instance.
How do I migrate data from the source ApsaraDB RDS for MySQL Enterprise Edition instance for which SSL encryption is enabled to the destination PolarDB-X 2.0 Standard Edition instance?
For information about how to migrate data from an ApsaraDB RDS for MySQL Enterprise Edition instance for which SSL encryption is enabled to a PolarDB-X 2.0 Standard Edition instance, see Procedure.
Note
If SSL encryption is enabled for the endpoints of the ApsaraDB RDS for MySQL Enterprise Edition instance and you select the Switch with Endpoints option to switch the endpoints, make sure that SSL encryption is enabled for the endpoints of the PolarDB-X 2.0 Standard Edition instance.
How do I migrate data from the source ApsaraDB RDS for MySQL Enterprise Edition instance to the destination PolarDB-X 2.0 Standard Edition instance if TDE is enabled for the source instance?
For information about how to migrate data from an ApsaraDB RDS for MySQL Enterprise Edition instance for which Transparent Data Encryption (TDE) is enabled to a PolarDB-X 2.0 Standard Edition instance, see Procedure.
Can I perform a cross-version migration, such as a migration from an ApsaraDB RDS for MySQL Enterprise Edition instance 5.6 to a PolarDB-X 2.0 Standard Edition instance 5.7?
Yes, you can perform a cross-version migration by using the logical migration method (DTS data synchronization).
If a Data Transmission Service (DTS) data synchronization task is started for the source ApsaraDB RDS for MySQL Enterprise Edition instance before I migrate data from the source instance to the destination PolarDB-X 2.0 Standard Edition instance, is the data synchronization task affected when I perform the migration?
No, the data synchronization task is not affected when you perform the migration. During the migration, full data is replicated from the source ApsaraDB RDS for MySQL Enterprise Edition instance to the new PolarDB-X 2.0 Standard Edition instance. Then, incremental data is synchronized from the source ApsaraDB RDS for MySQL Enterprise Edition instance to the PolarDB-X 2.0 Standard Edition instance in real time. The data source of the data synchronization task is still the source instance. Data synchronization to the destination instance does not affect the running of the source instance and operations performed on the source instance. However, after the migration is complete, if you switch over your business to the destination instance and the source instance stops providing services, the data source of the task does not automatically change to the destination instance. In this case, re-create a DTS data synchronization task and change the data source to the destination instance.