Migrate data between RDS MariaDB instances - Data Transmission Service

Data Transmission Service (DTS) supports data migration between RDS MariaDB instances.

Prerequisites

You have created a destination RDS MariaDB instance. For more information, see Create an RDS MariaDB instance.
The storage space of the destination RDS MariaDB instance must be larger than the storage space occupied by the source RDS MariaDB instance.

Precautions

Note

During schema migration, DTS migrates foreign keys from the source database to the destination database.
During full data migration and incremental data migration, 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 migration, data inconsistency may occur.

Category	Description
Source database limits	Bandwidth requirements: The server that hosts the source database must have sufficient outbound bandwidth. Otherwise, the data migration speed is affected. The tables to be migrated must have primary keys or UNIQUE constraints, and the fields in the tables must be unique. Otherwise, duplicate data may exist in the destination database. If you select tables as the migration objects and want to edit the tables, such as by mapping table or column names, you can migrate a maximum of 1,000 tables in a single data migration task. If the number of tables exceeds the limit, a request error is reported after you submit the task. In this case, split the tables to be migrated and configure multiple tasks to migrate the tables in batches, or configure a task to migrate the entire database. If you want to perform incremental migration, the following requirements for binary logs must be met: Binary logging must be enabled. The binlog_format parameter must be set to row, and the binlog_row_image parameter must be set to full. Otherwise, an error is reported during the precheck, and the data migration task cannot be started. If you perform an incremental data migration task, DTS requires that the binary logs of the source database be retained for more than 24 hours. If you perform a full and incremental data migration task, DTS requires that the binary logs of the source database be retained for at least 7 days. You can set the retention period of binary logs to more than 24 hours after full migration is complete. Otherwise, DTS may fail to obtain the binary logs, which causes the task to fail. In extreme cases, data inconsistency or data loss may occur. Issues that are caused because the retention period of binary logs that you set is shorter than the period required by DTS are not covered by the DTS Service-Level Agreement (SLA). During schema migration and full data migration, do not perform DDL operations to change the schemas of databases or tables. Otherwise, the data migration task fails. Note During full data migration, DTS queries the source database. This generates metadata locks, which may block DDL operations on the source database. If you perform only full data migration, do not write new data to the source database. Otherwise, data inconsistency occurs between the source and destination databases. To maintain real-time data consistency, select Schema Migration, Full Data Migration, and Incremental Data Migration.
Other limits	Before you migrate data, evaluate the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. During full data migration, DTS consumes read and write resources of the source and destination databases. This may increase the database load. During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination database. After full data migration is complete, the table storage space of the destination database is larger than that of the source instance. Make sure that the migration precision of columns of the FLOAT or DOUBLE data type meets your business requirements. DTS uses the `ROUND(COLUMN,PRECISION)` function to read the values of these two types of columns. If the precision is not explicitly defined, DTS sets the migration precision to 38 for the FLOAT data type and 308 for the DOUBLE data type. DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads to the destination database, you must stop or release the failed tasks. You can also execute the `REVOKE` statement to revoke the write permissions from the accounts that are used by DTS to access the destination database. Otherwise, the data in the source database overwrites the data in the destination database after a failed task is resumed. If DDL statements fail to be written to the destination database, the DTS task continues to run. You must view the failed DDL statements in the task logs. For more information about how to view task logs, see Query task logs. Make sure that the source and destination databases do not have invisible columns. Otherwise, the DTS instance may fail or data may be lost. If an instance fails, DTS helpdesk will try to recover the instance within 8 hours. During the recovery process, operations such as restarting the instance and adjusting parameters may be performed. Note When parameters are adjusted, only the parameters of the DTS instance are modified. The parameters of the database are not modified. The parameters that may be modified include but are not limited to those described in Modify instance parameters.
Special cases	When the destination database is an RDS MariaDB instance DTS automatically creates a database in the RDS MariaDB instance. If the name of the database to be migrated does not comply with the naming conventions of RDS MariaDB, you must create a database in the RDS MariaDB instance before you configure the data migration task. For more information, see Create a database and an account.

Billing

Migration type	Link configuration fee
Full data migration	Free of charge.
Incremental data migration	Charged. For more information, see Billing overview.

Migration type descriptions

Schema migration
DTS migrates the schema definitions of migration objects from the source database to the destination database.
Full migration
DTS migrates all historical data of migration objects from the source database to the destination database.
Incremental migration
After full migration, DTS migrates incremental data updates from the source database to the destination database. Incremental data migration lets you migrate data smoothly without stopping your self-managed applications.

SQL operations that can be incrementally migrated

Operation type	SQL statement
DML	INSERT, UPDATE, and DELETE
DDL	ALTER TABLE and ALTER VIEW CREATE FUNCTION, CREATE INDEX, CREATE PROCEDURE, CREATE TABLE, and CREATE VIEW DROP INDEX and DROP TABLE RENAME TABLE Important RENAME TABLE operations may cause data inconsistency between the source and destination databases. For example, if you select a table as the object to be migrated and rename the table during data migration, the data of this table is not migrated to the destination database. To prevent this situation, you can select the database to which this table belongs as the object to be migrated when you configure the data migration task. Make sure that the databases to which the table belongs before and after the RENAME TABLE operation are added to the objects to be migrated. TRUNCATE TABLE

Permissions required for database accounts

Database	Schema migration	Full migration	Incremental migration
Source RDS MariaDB instance	SELECT permission	SELECT permission	Read and write permissions
Destination RDS MariaDB instance	Read and write permissions	Read and write permissions	Read and write permissions

For more information about how to create a database account and grant permissions in an RDS MariaDB instance, see Create an account and Modify or reset account permissions.

Procedure

Use one of the following methods to go to the Data Migration page and select the region in which the data migration instance resides.
DTS console
1. Log on to the DTS console.
2. In the left-side navigation pane, click Data Migration.
3. In the upper-left corner of the page, select the region in which the data migration instance resides.
DMS console
Note
The actual operation may vary based on the mode and layout of the 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 > DTS (DTS) > Data Migration.
3. From the drop-down list to the right of Data Migration Tasks, select the region in which the data synchronization instance resides.
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.

Category	Configuration	Description
None	Task Name	DTS automatically generates a task name. Set a descriptive name to easily identify the task. The name does not need to be unique.
Source Database	Select Existing Connection	If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections. Note In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list. If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.
	Database Type	Select Mariadb.
	Access Method	Select Cloud Instance.
	Instance Region	Select the region where the source RDS MariaDB instance resides.
	Replicate Data Across Alibaba Cloud Accounts	This example shows how to migrate data within the same Alibaba Cloud account. Select No.
	Instance ID	Select the ID of the source RDS MariaDB instance.
	Database Account	Enter the database account of the source RDS MariaDB instance. For information about the required permissions, see Permissions required for database accounts.
	Database Password	The password that is used to access the database instance.
	Encryption	The default connection method for an RDS MariaDB instance is Non-encrypted Connection.
Destination Database	Select Existing Connection	If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections. Note In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list. If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.
	Database Type	Select Mariadb.
	Access Method	Select Cloud Instance.
	Instance Region	Select the region where the destination RDS MariaDB instance resides.
	RDS Instance ID	Select the ID of the destination RDS MariaDB instance.
	Database Account	Enter the database account of the destination RDS MariaDB instance.
	Database Password	The password that is used to access the database instance.
	Encryption	The default connection method for an RDS MariaDB instance is Non-encrypted Connection.

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 DTS server IP addresses to a whitelist.
- If the source or destination 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 migrated.

On the Configure Objects page, configure the objects that you want to migrate.

Configuration	Description
Migration Types	To perform only full data migration, select Schema Migration and Full Data Migration. To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Schema Migration, make sure a database and a table are created in the destination database to receive data and the object name mapping feature is enabled in Selected Objects. If you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
Method to Migrate Triggers in Source Database	Select a method to migrate triggers as needed. If no triggers are to be migrated, you do not need to configure this parameter. For more information, see Configure how to synchronize or migrate triggers. Note This parameter is available only if you select Schema Migration for the Migration Types parameter.
Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains tables that use 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 migration 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 migrated 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 the following potential risks: If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database, the following scenarios may occur: During full data migration, DTS does not migrate the data record to the destination database. The existing data record in the destination database is retained. During incremental data migration, DTS migrates 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, only specific columns are migrated or the data migration task fails. Proceed with caution.
Source Objects	Select one or more objects from the Source Objects section. Click the icon and add the objects to the Selected Objects section. Note You can select columns, tables, or databases as the objects to be migrated. If you select tables or columns as the objects to be migrated, DTS does not migrate other objects, such as views, triggers, or stored procedures, to the destination database.
Selected Objects	To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object. To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time. Note If you use the object name mapping feature, other objects that depend on the mapped object may fail to be migrated. To specify a WHERE clause to filter data, right-click a table in the Selected Objects box and specify the clause in the dialog box that appears. For more information, see Set filter conditions. To select the SQL operations to be migrated at the database or table level, right-click a migration object in the Selected Objects box and select the SQL operations in the dialog box that appears.

Click Next: Advanced Settings to configure advanced settings.

Configuration	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules the data migration task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data migration tasks, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.
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 migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1,440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later 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 the earliest opportunity after the source database and destination instance are released.
Retry Time for Other Issues	The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration 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	Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must 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. This reduces the loads of the destination database server. Note You can configure this parameter only if you select Full Data Migration for the Migration Types parameter.
Enable Throttling for Incremental Data Migration	Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server. Note You can configure this parameter only if you select Incremental Data Migration for the Migration Types parameter.
Environment Tag	You can select an environment tag to identify the instance. In this example, you do not need to select a tag.
Configure ETL	Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: configures the ETL feature. You can enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: does not configure the ETL feature.
Monitoring and Alerting	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values: No: does not configure 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.

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 migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.
- If the task fails to pass the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.
- 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 issues. Then, run a precheck again.
  If the 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.

Purchase the instance.

Wait until Success Rate becomes 100%. Then, click Next: Purchase Instance.

On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

Section	Parameter	Description
New Instance Class	Resource Group	The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Instance classes of data migration instances.

Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.
Click Buy and Start. In the message that appears, click OK.
You can view the progress of the task on the Data Migration page.
Note
- If a data migration task cannot be used to migrate incremental data, the task automatically stops. The Completed is displayed in the Status section.
- If a data migration task can be used to migrate incremental data, the task does not automatically stop. The incremental data migration task never stops or completes. The Running is displayed in the Status section.