This topic answers frequently asked questions (FAQ) for Data Transmission Service (DTS).

Which databases does DTS support in data migration, data synchronization, and change tracking?

DTS supports data transmission between various data sources, such as relational database management systems (RDBMS), NoSQL databases, and online analytical processing (OLAP) databases. For more information, see Databases supported by DTS features.

Note DTS also supports data migration and synchronization from databases that are provided by third-party cloud vendors to Alibaba Cloud. For more information, see Overview of data migration scenarios.

How does data migration, data synchronization, and change tracking work?

For more information, see System architecture and design concepts.

What are the differences between data migration and data synchronization?

Item Data migration Data synchronization
Scenarios The data migration feature is used to migrate data from on-premises databases, user-created databases hosted on ECS, and databases on third-party cloud platforms to Alibaba Cloud.

You can release a data migration task immediately after it is complete.

The data synchronization feature is used to synchronize data between two data sources in real time. It is suitable for scenarios such as active geo-redundancy, disaster recovery, cross-border data synchronization, query load balancing, cloud BI systems, and real-time data warehousing.

After you create a data synchronization task, it continuously synchronizes data between the specified data sources to ensure data consistency.

Supported databases For more information, see Databases supported by DTS features. For more information, see Databases supported by DTS features.
Supported deployment locations of databases
  • User-created database with a public IP address
  • User-created database hosted on ECS
  • User-created database connected over Express Connect, VPN Gateway, or Smart Access Gateway
  • User-created database hosted on ECS
  • User-created database connected over Express Connect, VPN Gateway, or Smart Access Gateway
Note The data synchronization feature ensures low network latency through data transmission over the internal network.
Features You can read and migrate data across user-created databases that are deployed on VPCs owned by different Alibaba cloud accounts.
  • You can change the names of objects such as columns, tables, and databases.
  • You can filter the data to be synchronized.
  • You can modify the objects to be synchronized.
  • You can configure two-way data synchronization between MySQL databases.
  • You can select the types of operations to be synchronized. For example, you can synchronize only INSERT operations.
Billing methods Only the pay-as-you-go billing method is supported. The pay-as-you-go and subscription billing methods are supported.
Billing rules You are billed when incremental data migration is in progress, including the period when incremental data migration is paused. You are not billed for schema migration and full data migration.
  • If you use the pay-as-you-go billing method, billing starts after the task is configured and started. You are also billed when the task is paused.
  • If you use the subscription billing method, the fee is deducted at the time of purchase based on the quantity and configurations you select.
Note For databases that are not supported by the data synchronization feature (such as databases on ApsaraDB for MongoDB instances), you can perform incremental data migration. Incremental data migration can ensure that data is synchronized between the source and destination database.

How is the synchronization delay measured?

The synchronization delay is the difference between the timestamp of the latest synchronized data in the destination database and the current timestamp in the source database. The unit is milliseconds.

What can I do if DTS cannot connect to the database?

For more information, see Source database connectivity and Destination database connectivity.

What is the billing method of DTS?

For more information, see Pricing.

What are the differences between different channel specifications?

For more information, see Specifications of data migration channels and Specifications of data synchronization channels.

Can channel specifications be downgraded?

No, channel specifications cannot be downgraded.

Why is the price of data synchronization higher than that of data migration?

Data synchronization comes with more advanced features. For example, you can modify the objects to be synchronized. You can configure two-way data synchronization between MySQL databases. In addition, the data synchronization feature ensures low network latency through data transmission over the internal network.

Can I migrate or synchronize data across Alibaba Cloud accounts?

Can I migrate data within a single instance?

Yes, you can migrate data within a single instance. For more information, see Migrate data between databases with different names.

Can I migrate or synchronize DML and DDL operations?

Yes, you can migrate or synchronize DML and DDL operations between relational databases. The supported DML operations are INSERT, UPDATE, and DELETE. The supported DDL operations are CREATE, DROP, ALTER, RENAME, and TRUNCATE.

Note The supported DML and DDL operations are different in different scenarios. For example, if you synchronize data from a MySQL database to AnalyticDB for MySQL 2.0, only the following DDL operations are supported: CREATE TABLE, ALTER TABLE, and DROP TABLE. Only the following DML operations are supported: INSERT, UPDATE, and DELETE. For more information, see the topics about data migration and synchronization scenarios.

Can I migrate or synchronize database shards and table shards?

Yes, you can migrate or synchronize database shards and table shards. For example, you can migrate or synchronize database shards and table shards from a MySQL database and Apsara PolarDB for MySQL cluster to AnalyticDB for MySQL. This allows you to merge multiple tables.

Can I migrate or synchronize data across time zones and character sets?

Yes, you can migrate or synchronize data across time zones and character sets.

Can I change the name of objects that are migrated or synchronized to the destination database?

Yes, you can change the name of columns, tables, and databases by using the object name mapping feature. For more information, see Object name mapping and Specify the name of an object in the destination instance.

Can I filter fields or data?

Yes, you can filter fields or data in a table. For more information, see Use conditions to filter data and Use SQL conditions to filter data.

Can I add or remove objects to be synchronized?

Yes, you can add or remove objects to be synchronized. For more information, see Add an object to a data synchronization task and Remove an object from a data synchronization task.

How do I view the performance of data migration and synchronization?

For more information, see Check the performance of incremental data migration and Check the synchronization performance.

How do I consume tracked data?