Synchronize an entire instance - Data Transmission Service

Data Transmission Service (DTS) allows you to synchronize MySQL databases deployed in data centers, on Elastic Compute Service (ECS) instances, or on other cloud platforms and all database and table data of ApsaraDB RDS for MySQL instances to an ApsaraDB RDS for MySQL instance. You can use a DTS instance to smoothly synchronize MySQL databases to Alibaba Cloud.

Important

This feature is in canary release and available only to specific customers.

Prerequisites

The MySQL database is connected to Alibaba Cloud if the MySQL database is deployed in a data center or on another cloud platform. For more information, see Preparation overview.
Note
For information about the supported versions of the source and destination databases, see Overview of data synchronization scenarios.
The destination ApsaraDB RDS for MySQL instance is created. The available storage space of the destination database is larger than the total size of data in the source self-managed MySQL database. For more information, see Create an ApsaraDB RDS for MySQL instance.

Usage notes

Note

During schema synchronization, DTS synchronizes foreign keys from the source database to the destination database.
During full data synchronization and incremental data synchronization, DTS temporarily disables the constraint check and cascade operations on foreign keys at the session level. If you perform the cascade update and delete operations on the source database during data synchronization, data inconsistency may occur.

Category	Description
Limits on the source database	The server to which the source database belongs must have a sufficient outbound bandwidth. Otherwise, the data synchronization speed is limited. The following requirements for binary logs must be met: By default, the binary logging feature is enabled for an ApsaraDB RDS for MySQL instance. Make sure that the binlog_row_image parameter is set to full. Otherwise, error messages are returned during the precheck and the data synchronization task cannot be started. For more information, see Modify instance parameters. Important If the source database is a self-managed MySQL database, you must enable the binary logging feature and set the binlog_format parameter to row and the binlog_row_image parameter to full. If the source database is a self-managed MySQL database deployed in a dual-primary cluster, you must set the log_slave_updates parameter to ON. This ensures that DTS can obtain all binary logs. For more information, see Create an account for a self-managed MySQL database and configure binary logging. The binary logs of the source database must be stored for at least seven days. Otherwise, the data synchronization task may fail because DTS cannot obtain the binary logs. In exceptional circumstances, data inconsistency or loss may occur. Make sure that you configure the retention period of binary logs based on the preceding requirements. Otherwise, the service reliability or performance in the Service Level Agreement (SLA) of DTS may not be guaranteed. For more information about how to manage the binary log files of an ApsaraDB RDS for MySQL instance, see Manage binary log files. During schema synchronization and full data synchronization, do not execute DDL statements to change the schemas of databases or tables. Otherwise, the data synchronization task fails.
Other limits	You can select only MySQL as the source Database Type, MySQL as the destination Database Type, and Alibaba Cloud Instance as the Access Method. Two-way synchronization DTS instances are not supported. Note You cannot use a two-way synchronization DTS instance to synchronize an entire instance. One-way synchronization DTS instances that are configured for synchronizing an entire instance cannot be converted to two-way synchronization DTS instances. You cannot select a synchronization type. By default, schema synchronization, full data synchronization, and incremental data synchronization are performed. You cannot select the objects to be synchronized, map object names, select SQL statements for incremental synchronization, configure WHERE clauses to filter data, or add additional columns. You cannot configure the extract, transform, and load (ETL) feature. Data verification is not supported. You cannot modify the objects to be synchronized. To ensure compatibility, the version of the destination database must be the same as or later than that of the source database. If the version of the destination instance is earlier than that of the source database, database compatibility issues may occur. During initial full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. Before you synchronize data, assess the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours, such as when the CPU usage of the source and destination databases is lower than 30%. During initial full data synchronization, concurrent INSERT operations cause table fragmentation in the destination database. Therefore, after initial full data synchronization is complete, the size of the used tablespace of the destination database is larger than that of the source database. During data synchronization, we recommend that you use only DTS to write data to the destination. This prevents data inconsistency between the source and destination. If DDL statements fail to be executed in the destination database, the DTS task continues to run. You can view the DDL statements that fail to be executed in task logs. For more information about how to view task logs, see View task logs. After data synchronization is complete, that is, the Status of the instance changes to Completed, we recommend that you run the `analyze table <Table name>` command to check whether data is written to the destination table. For example, if a high-availability (HA) switchover is triggered in the source MySQL database, data may be written only to the memory. As a result, data loss occurs. If the source database is an ApsaraDB RDS for MySQL instance for which the EncDB feature is enabled, full data synchronization cannot be performed. Note ApsaraDB RDS for MySQL instances that have the Transparent Data Encryption (TDE) feature enabled support schema synchronization, full data synchronization, and incremental data synchronization. If a DTS task fails to run, DTS technical support will try to restore the task within 8 hours. During the restoration, the task may be restarted, and the parameters of the task may be modified. Note Only the parameters of the task may be modified. The parameters of databases are not modified. The parameters that may be modified include but are not limited to the parameters in the "Modify instance parameters" section of the Modify the parameters of a DTS instance topic.
Special cases	If the source database is a self-managed MySQL database, take note of the following items: If you perform a primary/secondary switchover on the source database when the data synchronization task is running, the task fails. DTS calculates synchronization latency based on the timestamp of the latest synchronized data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for a long time, the synchronization latency may be inaccurate. If the latency of the data synchronization task is too high, you can perform a DML operation on the source database to update the latency. Note If you select an entire database as the object to synchronize, you can create a heartbeat table. The heartbeat table is updated or receives data every second. DTS executes the CREATE DATABASE IF NOT EXISTS 'test' statement in the source database as scheduled to move forward the binary log file position. If the source database is an ApsaraDB RDS for MySQL instance, take note of the following item: An ApsaraDB RDS for MySQL instance that does not record transaction logs, such as a read-only ApsaraDB RDS for MySQL 5.6 instance, cannot be used as the source database. DTS executes the CREATE DATABASE IF NOT EXISTS 'test' statement in the source database as scheduled to move forward the binary log file position.

Billing

Synchronization type	Task configuration fee
Schema synchronization and full data synchronization	Free of charge.
Incremental data synchronization	Charged. For more information, see Billing overview.

SQL operations that can be synchronized

Operation type	SQL statement
DML	INSERT, UPDATE, and DELETE
DDL	ALTER TABLE and ALTER VIEW CREATE DATABASE, CREATE FUNCTION, CREATE INDEX, CREATE PROCEDURE, CREATE TABLE, and CREATE VIEW DROP DATABASE, DROP INDEX, and DROP TABLE RENAME TABLE TRUNCATE TABLE

Permissions required for database accounts

Database type		Required permissions	References
Source database	Self-managed MySQL database	The SELECT permission on the objects to be synchronized. The REPLICATION CLIENT permission, REPLICATION SLAVE permission, and SHOW VIEW permission. The permissions to create databases and tables.	Create an account for a self-managed MySQL database and configure binary logging
Source database	RDS MySQL	Read and write permissions.	Create an account and Modify account permissions
Destination database	RDS MySQL	Read and write permissions.	Create an account and Modify account permissions

Note

If the source database is an ApsaraDB RDS for MySQL instance and the source database account that you use is not created and authorized in the ApsaraDB RDS for MySQL console, make sure that the account has the REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT permissions.
If you want to synchronize the account information of the source database, additional permissions are required for the source and destination database accounts. For more information, see Migrate database accounts.

Procedure

Use one of the following methods to go to the Data Synchronization page and select the region in which the data synchronization instance resides.
DTS console
1. Log on to the DTS console.
2. In the left-side navigation pane, click Data Synchronization.
3. In the upper-left corner of the page, select the region in which the data synchronization instance resides.
DMS console
Note
The actual operations may vary based on the mode and layout of the Data Management (DMS) console. For more information, see Simple mode and Customize the layout and style of the DMS console.
1. Log on to the DMS console.
2. In the top navigation bar, move the pointer over Data + AI and choose DTS (DTS) > Data Synchronization.
3. On the right side of Data Synchronization Tasks, select the region in which your synchronization instance resides from the drop-down list.
Click Create Task to go to the task configuration page.
Optional. Click New Configuration Page in the upper-right corner of the page.
Note
- Skip this step if the Back to Previous Version button is displayed in the upper-right corner of the page.
- Specific parameters in the new and previous versions of the configuration page may be different. We recommend that you use the new version of the configuration page.

Configure the source and destination databases. The following table describes the parameters.

Section	Parameter	Description
N/A	Task Name	The name of the DTS task. DTS automatically generates a task name. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.
Source Database	Select Existing Connection	The database that you want to use. You can choose whether to use an existing database based on your business requirements. If you select an existing database, DTS automatically populates the parameters for the database. If you do not select an existing database, you must configure the following database information. Note In the DTS console, register a database with DTS on the Database Connections page or the new configuration page. For more information, see Manage database connections. In the DMS console, you can select an existing database from the Select a DMS database instance. drop-down list. You can also click Add DMS Database Instance or go back to the homepage of the DMS console to register a database with DMS. For more information, see Register an Alibaba Cloud database instance and Register a database hosted on a third-party cloud service or a self-managed database.
	Database Type	The type of the source database. Select MySQL.
	Access Method	The access method of the source database. Select an access method based on your business requirements. In this example, Express Connect, VPN Gateway, or Smart Access Gateway is selected.
	Instance Region	The region in which the virtual private cloud (VPC) of the self-managed MySQL database resides.
	Replicate Data Across Alibaba Cloud Accounts	In this example, a database of the current Alibaba Cloud account is used. Select No.
	Connected VPC	The ID of the VPC that is connected to the self-managed MySQL instance.
	Domain Name or IP	The IP address or domain name of the self-managed MySQL database server.
	Port Number	The service port number of the self-managed MySQL database. The default port number is 3306.
	Database Account	The database account of the source ApsaraDB RDS for MySQL instance. For more information about the permissions that are required for the account, see the "Permissions required for database accounts" section of this topic.
	Database Password	The password that is used to access the database.
	Encryption	Specifies whether to encrypt the connection to the database. You can select Non-encrypted or SSL-encrypted based on your business requirements. If you want to set this parameter to SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the DTS task. For more information, see Use a cloud certificate to enable SSL encryption.
Destination Database	Select Existing Connection	The database that you want to use. You can choose whether to use an existing database based on your business requirements. If you select an existing database, DTS automatically populates the parameters for the database. If you do not select an existing database, you must configure the following database information. Note In the DTS console, register a database with DTS on the Database Connections page or the new configuration page. For more information, see Manage database connections. In the DMS console, you can select an existing database from the Select a DMS database instance. drop-down list. You can also click Add DMS Database Instance or go back to the homepage of the DMS console to register a database with DMS. For more information, see Register an Alibaba Cloud database instance and Register a database hosted on a third-party cloud service or a self-managed database.
	Database Type	The type of the destination database. Select MySQL.
	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
	Instance Region	The region in which the destination ApsaraDB RDS for MySQL instance resides.
	Replicate Data Across Alibaba Cloud Accounts	In this example, a database of the current Alibaba Cloud account is used. Select No.
	RDS Instance ID	The ID of the destination ApsaraDB RDS for MySQL instance.
	Database Account	The database account of the ApsaraDB RDS for MySQL instance. For more information about the permissions that are required for the database account, see the "Permissions required for database accounts" section of this topic.
	Database Password	The password that is used to access the database.
	Encryption	Specifies whether to encrypt the connection to the database. You can select Non-encrypted or SSL-encrypted based on your business requirements. If you want to set this parameter to SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the DTS task. For more information, see Use a cloud certificate to enable SSL encryption.

In the lower part of the page, click Test Connectivity and Proceed.
Note
- Make sure that the CIDR blocks of DTS servers can be automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add the CIDR blocks of DTS servers.
- If the source database is a self-managed database and its Access Method is not set to Alibaba Cloud Instance, click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

Configure the objects to be synchronized.

On the Configure Objects page, set the Select Objects parameter to Synchronize Entire Instance and configure the other parameters.

Parameter	Description
Synchronization Types	By default, Schema Synchronization, Full Data Synchronization, and Incremental Data Synchronization are selected and cannot be cleared.
Method to Migrate Triggers in Source Database	The method used to synchronize triggers from the source database. You can select a synchronization method based on your business requirements. If no triggers are to be synchronized, you do not need to configure this parameter. For more information, see Synchronize or migrate triggers from the source database. Note This parameter is available only if you select Schema Synchronization for the Synchronization Types parameter.
Enable Migration Assessment	Specifies whether to enable synchronization assessment. You can check whether the schemas of the source and destination databases, such as the length of indexes, stored procedures, and dependent tables, meet the requirements. Select Yes or No based on your business requirements. Note This parameter is displayed only if the Schema Synchronization parameter is set to Synchronization Types. If you select Yes, the precheck time may increase. You can view the assessment results during the precheck. The Assessment Result do not affect the precheck results.
Synchronization Topology	The synchronization topology. By default, One-way Synchronization is selected and cannot be cleared.
Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck, and the data synchronization task cannot be started. Note If the source and destination databases contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are synchronized to the destination database. For more information, see Map object names. Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases. Warning If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to potential risks. If the source and destination databases have the same schema and a data record in the destination database has the same primary key value or unique key value as a data record in the source database: During full data synchronization, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained. During incremental data synchronization, DTS synchronizes the data record to the destination database. The existing data record in the destination database is overwritten. If the source and destination databases have different schemas, data may fail to be initialized. In this case, only some columns are synchronized, or the data synchronization task fails. Proceed with caution.
Capitalization of Object Names in Destination Instance	The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to ensure that the capitalization of object names is consistent with that in the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.
Selected Objects	Retain the default settings.

Click Next: Advanced Settings to configure advanced settings.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules the task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data synchronization tasks, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.
Copy the temporary table of the Online DDL tool that is generated in the source table to the destination database.	If you use DMS or the gh-ost tool to perform online DDL operations on the source database, you can specify whether to synchronize the data of temporary tables generated by online DDL operations. Important You cannot use tools such as pt-online-schema-change to perform online DDL operations on the source database. Otherwise, the DTS task fails. Yes: DTS synchronizes the data of temporary tables generated by online DDL operations. Note If online DDL operations generate a large amount of data, the data synchronization task may take an extended period of time to complete. No, Adapt to DMS Online DDL: DTS does not synchronize the data of temporary tables generated by online DDL operations. Only the original DDL operations that are performed by using DMS are synchronized. Note If you select this option, the tables in the destination database may be locked. No, Adapt to gh-ost: DTS does not synchronize the data of temporary tables generated by online DDL operations. Only the original DDL operations that are performed by using the gh-ost tool are synchronized. You can use the default or custom regular expressions to filter out the shadow tables of the gh-ost tool and tables that are not required. Note If you select this option, the tables in the destination database may be locked.
Whether to Migrate Accounts	Specifies whether to synchronize the account information of the source database based on your business requirements. If you select Yes, you must select the accounts to be synchronized and check their permissions.
Retry Time for Failed Connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data synchronization task is started, DTS immediately retries a connection within the time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set this parameter to a value greater than 30. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails. Note If you specify different retry time ranges for multiple data synchronization tasks that have the same source or destination database, the shortest retry time range takes precedence. When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
Retry Time for Other Issues	The retry time range for other issues. For example, if the DDL or DML operations fail to be performed after the data synchronization task is started, DTS immediately retries the operations within the time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set this parameter to a value greater than 10. If the failed operations are successfully performed within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails. Important The value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
Enable Throttling for Full Data Migration	During full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the load on the database servers. You can configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters for full data synchronization tasks to reduce the load on the destination database server. Note This parameter is displayed only if Full Data Synchronization is selected for the Synchronization Types parameter.
Enable Throttling for Incremental Data Synchronization	Specifies whether to enable throttling for incremental data synchronization. You can enable throttling for incremental data synchronization based on your business requirements. To configure throttling, you must configure the RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s) parameters. This reduces the load on the destination database server.
Whether to delete SQL operations on heartbeat tables of forward and reverse tasks	Specifies whether to write SQL operations on heartbeat tables to the source database while the DTS instance is running. Valid values: Yes: does not write SQL operations on heartbeat tables. In this case, a latency of the DTS instance may be displayed. No: writes SQL operations on heartbeat tables. In this case, features such as physical backup and cloning of the source database may be affected.
Environment Tag	The environment tag that is used to identify the instance. You can select an environment tag based on your business requirements. In this example, you do not need to configure this parameter.
Monitoring and Alerting	Specifies whether to configure alerting for the data synchronization task. If the task fails or the synchronization latency exceeds the specified threshold, alert contacts will receive notifications. Valid values: No: does not enable alerting. Yes: configures alerting. In this case, you must also configure the alert threshold and alert notification settings. For more information, see the "Configure monitoring and alerting when you create a DTS task" section of the Configure monitoring and alerting topic.

Click Next Step: Data Verification.
If you synchronize an entire instance, the data verification feature is not supported. This step is skipped.

Save the task settings and run a precheck.
- To view the parameters to be specified when you call the relevant API operation to configure the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.
- If you do not need to view or have viewed the parameters, click Next: Save Task Settings and Precheck in the lower part of the page.
Note
- Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.
- If the data synchronization task fails the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, rerun the precheck.
- If an alert is triggered for an item during the precheck:
  If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issue. Then, run a precheck again.
  If an alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.
Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.

Purchase a data synchronization instance.

On the buy page, configure the Billing Method and Instance Class parameters for the data synchronization instance. The following table describes the parameters.

Section	Parameter	Description
New Instance Class	Billing Method	Subscription: You pay for a subscription when you create a data synchronization instance. The subscription billing method is more cost-effective than the pay-as-you-go billing method for long-term use. Pay-as-you-go: A pay-as-you-go instance is billed on an hourly basis. The pay-as-you-go billing method is suitable for short-term use. If you no longer require a pay-as-you-go data synchronization instance, you can release the instance to reduce costs.
	Resource Group Settings	The resource group to which the data synchronization instance belongs. Default value: default resource group. For more information, see What is Resource Management?
	Instance Class	DTS provides instance classes that vary in synchronization speed. You can select an instance class based on your business requirements. For more information, see Instance classes of data synchronization instances.
	Subscription Duration	If you select the subscription billing method, specify the subscription duration and the number of data synchronization instances that you want to create. The subscription duration can be one to nine months, one year, two years, three years, or five years. Note This parameter is available only if you select the Subscription billing method.

Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the dialog box that appears, click OK.
You can view the progress of the task in the task list.