Impact on the Source Database
When Data Transfer Service (DTS) is used to perform a full data migration, it occupies certain resources of the source instance, which may cause the source instance load to increase and add pressure to the database. If your database configuration is low, it is recommended to perform the migration during off-peak hours.
Migration Limitations and Instructions
1. To avoid impacting the source business instance during data migration, DTS tasks migrate data through Redis replica nodes by default. If replica node rebuild occurs on the source Redis during migration, DTS task recovery waits for the replica node rebuild to complete before retrying, which may cause full data to be migrated to the target end again. Therefore, it is recommended that you configure task interruption alarms and retry policies to promptly check task status and take appropriate actions.
2. The source instance can only be migrated when it is in normal operation. Migration cannot be performed when the password is uninitialized or when other tasks (such as scale-out) are in progress.
3. DTS tasks shall not form a circular synchronization. The data written in circular synchronization will not be terminated and will keep running in the loop, which will lead to an infinite write loop.
4. DTS supports resumable transfer at the source end in the event of network jitter.
5. Migration of modules is not supported.
6. If global replication is enabled for Tencent Cloud Distributed Cache, DTS only supports selecting a primary instance when connecting to the source database.
7. Do not perform the following operations during migration. Otherwise, they will cause the migration task to fail.
Do not modify or delete user information (including usernames, passwords, and permissions) and port numbers in the source and target databases.
Do not delete the target database during the data migration phase.
Do not perform operations on the target database data during the data migration phase to avoid data inconsistency.
8. During the migration, data inconsistency may occur if the following events occur (including but not limited to):
A primary/secondary switchover or failover occurs on the source or target side.
The connection address of the source or target side changes.
9. If the nodes in the source instance of the migration task do not belong to the same Redis cluster, the check task cannot run successfully.
10. If the target instance of the DTS task is read-only, do not perform operations such as backup, shard expansion, or shard reduction on the target database before clicking Complete or Terminate for the migration task. Otherwise, the read/write attribute of the target database cannot be changed in time.