This topic describes how to migrate data from an ApsaraDB RDS for MySQL instance to an AnalyticDB for MySQL V3.0 cluster by using Data Transmission Service (DTS). After you migrate data, you can use AnalyticDB for MySQL to build internal business intelligence (BI) systems, interactive query systems, and real-time report systems.

Prerequisites

  • The destination AnalyticDB for MySQL V3.0 cluster is created. For more information, see Create a cluster.
  • The available storage space of the destination AnalyticDB for MySQL cluster is larger than the total size of the data in the source ApsaraDB RDS for MySQL instance.

Limits

Category Description
Limits on the source database
  • Bandwidth requirements: The server to which the source database belongs must have sufficient egress bandwidth. Otherwise, the data migration speed is affected.
  • The tables to be migrated must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
  • If you select tables as the objects to be migrated and you need to edit tables (such as rename tables or columns), up to 1,000 tables can be migrated in a single data migration task. If you run a task to migrate more than 1,000 tables, a request error occurs. In this case, we recommend that you split the tables to be migrated, configure multiple tasks to migrate the tables, or call DTS API operations to configure tasks.
  • If you want to migrate incremental data, you must make sure that the following requirements are met:
    • The binary logging feature must be enabled. The value of the binlog_format parameter must be set to row. The value of the binlog_row_image parameter must be set to full. Otherwise, error messages are returned during precheck and the data migration task cannot be started.
    • Binary logs are retained for at least 7 days during full data migration. You can wait until full data migration is complete, and then clear the binary logs generated in the source database after the DTS task is run.
      Note DTS stores only 50 GB of binary logs or the binary logs for the last 24 hours. If the limit is exceeded, DTS automatically clears the cached logs.
      Warning If you clear the binary logs of the source database during full data migration, the data migration task may fail. For example, full data migration takes more than 24 hours due to the large data volume in the source database and abnormal writing in the destination database. In this case, if the binary logs of the source database are cleared during full data migration, DTS cannot obtain the binary logs generated 24 hours ago. Therefore, the data migration task may fail.
  • Limits on operations:
    • During schema migration and full data migration, do not perform data definition language (DDL) operations to change the schemas of databases or tables. Otherwise, the data migration task fails.
    • During data migration, do not perform DDL operations to add comments, for example, ALTER TABLE table_name COMMENT='Table comment';. Otherwise, the data migration task fails.
    • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data will be inconsistent between the source and destination databases. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types.
Other limits
  • Prefix indexes cannot be migrated. If the source database contains prefix indexes, data may fail to be migrated.
  • Due to the limits of AnalyticDB for MySQL, if the disk space usage of the nodes in an AnalyticDB for MySQL cluster reaches 80%, the task is delayed and error messages are returned. We recommend that you estimate the required disk space based on the objects that you want to migrate. You must make sure that the destination cluster has sufficient storage space.
  • Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. During full data migration, DTS uses read and write resources of the source and destination databases. This may increase the loads of the database servers.
  • During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination database. After full data migration is complete, the tablespace of the destination database is larger than that of the source database.
  • You must make sure that the precision settings for columns of the FLOAT or DOUBLE data type meets your business requirements. DTS uses the ROUND(COLUMN,PRECISION) function to retrieve values from columns of the FLOAT or DOUBLE data type. If you do not specify a precision, DTS sets the precision for the FLOAT data type to 38 digits and the precision for the DOUBLE data type to 308 digits.
  • DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads to the destination instance, stop or release the data migration task. You can also run the revoke command to revoke the write permissions from the accounts that are used by DTS to access the destination instance. Otherwise, the data in the source database will overwrite the data in the destination instance after the task is resumed.
Special cases
If the source database is a self-managed MySQL database, take note of the following limits:
  • If you perform a primary/secondary switchover on the source database when the data migration task is running, the task fails.
  • DTS calculates migration latency based on the timestamp of the latest migrated data in the destination database and the current timestamp in the source database. If no data manipulation language (DML) operation is performed on the source database for a long time, the migration latency may be inaccurate. If the latency of the migration 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 be migrated, you can create a heartbeat table. The heartbeat table is updated or receives data every second.

Billing

Migration type Task configuration fee Internet traffic fee
Schema migration and full data migration Free of charge. Charged only when data is migrated from Alibaba Cloud over the Internet. For more information, see Pricing.
Incremental data migration Charged. For more information, see Pricing.

Migration types

  • Schema migration

    DTS migrates the schemas of the required objects from the source database to the destination database.

    Note ApsaraDB RDS for MySQL and AnalyticDB for MySQL are heterogeneous databases. DTS does not ensure that the schemas of the source and destination databases are consistent after schema migration. We recommend that you evaluate the impact of data type conversion on your business. For more information, see Data type mappings between heterogeneous databases.
  • Full data migration

    DTS migrates historical data of the required objects from the source database to the destination database.

  • Incremental data migration

    After full data migration is complete, DTS synchronizes incremental data from the source database to the destination database. Incremental data migration allows you to ensure service continuity when you migrate data between self-managed databases.

SQL operations that can be migrated

Operation type SQL statements
DML INSERT, UPDATE, and DELETE
DDL CREATE TABLE, DROP TABLE, RENAME TABLE, TRUNCATE TABLE, ADD COLUMN, and DROP COLUMN
Warning If the data type of a field in the source table is changed during data migration, an error message is generated and the data migration task is stopped. You can submit a ticket or perform the following steps to troubleshoot the issue.
  1. When DTS migrates data to the destination AnalyticDB for MySQL cluster, the data type of a field named customer in the source table is changed. As a result, the data migration task fails.
  2. In the destination AnalyticDB for MySQL V3.0 cluster, create a table named customer_new. The customer_new table has the same schema as the customer table.
  3. Run the INSERT INTO SELECT command to copy the data of the customer table and insert the data into the customer_new table. This ensures that the data of the two tables is consistent.
  4. Rename or delete the customer table. Then, change the name of the customer_new table to customer.
  5. Restart the data migration task in the DTS console.

Permissions required for database accounts

Database Schema migration Full data migration Incremental data migration
ApsaraDB RDS for MySQL The SELECT permission The SELECT permission The SELECT permission on the objects to be migrated, the REPLICATION SLAVE permission, and the REPLICATION CLIENT permission. DTS automatically grants these permissions to the database account.
AnalyticDB for MySQL V3.0 The read and write permissions
For more information about how to create and authorize a database account, see the following topics:

Procedure

  1. Go to the Data Migration page of the new DTS console.
    Note You can also log on to the Data Management (DMS) console. In the top navigation bar, choose DTS > Data Migration.
  2. In the upper-left corner of the page, select the region where the data migration instance resides.
    Select a region
  3. Click Create Task. On the page that appears, configure the source and destination databases.
    Warning After you select the source and destination instances, we recommend that you read the limits displayed at the top of the page. This ensures that you can create and run the data migration task.
    Configure the source and destination databases
    Section Parameter Description
    N/A Task Name

    DTS automatically generates a task name. We recommend that you specify an informative name that helps identify the task. The task name does not need to be unique.

    Source Database Database Type Select MySQL.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select the region where the source ApsaraDB RDS for MySQL instance resides.
    Replicate Data Across Alibaba Cloud Accounts In this example, select No because data is migrated within the same Alibaba Cloud account.
    RDS Instance ID Select the ID of the source ApsaraDB RDS for MySQL instance.
    Database Account Enter the database account of the source ApsaraDB RDS for MySQL instance. For information about the permissions that are required for the account, see Permissions required for database accounts.
    Database Password

    Enter the password of the database account.

    Destination Database Database Type Select AnalyticDB for MySQL 3.0.
    Access Method Select Alibaba Cloud Instance.
    Instance Region Select the region where the destination AnalyticDB for MySQL V3.0 cluster resides.
    Instance ID Select the ID of the destination AnalyticDB for MySQL V3.0 cluster.
    Database Account Enter the database account of the destination AnalyticDB for MySQL V3.0 cluster. For information about the permissions that are required for the account, see Permissions required for database accounts.
    Database Password

    Enter the password of the database account.

  4. In the lower part of the page, click Test Connectivity and Proceed.
  5. Select objects for the task and configure advanced settings.
    • Basic SettingsBasic Settings (Merge Tables + Select SQL Operations)
      Parameter Description
      Task Stages
      • 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 Incremental Data Migration is not selected, we recommend that you do not write data to the source instance during data migration. This ensures data consistency between the source and destination instances.
      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 identical table names, the precheck is passed. Otherwise, an error is returned during precheck and the data migration task cannot be started.
        Note You can use the object name mapping feature to rename the tables that are migrated to the destination database. You can use this feature if the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed.
      • 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 consistency is not guaranteed and your business may be exposed to potential risks.
        • If the source and destination databases have the same schema, DTS does not migrate data records that have the same primary keys as data records in the destination database.
        • If the source and destination databases have different schemas, only some columns are migrated or the data migration task fails.
      DDL and DML Operations to Be Synchronized Select the SQL operations that you want to migrate at the instance level. For more information, see SQL operations that can be migrated
      Note To select the SQL operations performed on a specific database or table, perform the following steps: In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to migrate.
      Merge Tables
      • If you select Yes, DTS adds the __dts_data_source column to each table to record data sources.
      • No is selected by default.
      Note If you set this parameter to Yes, all of the selected source tables in the task are merged into the destination table. To merge only the data source columns of specific tables, you can create two data migration tasks.
      Warning We recommend that you do not perform DDL operations to change the schemas of source databases or tables. Otherwise, data inconsistency may occur or the migration task fails.
      Select Objects

      Select one or more objects from the Source Objects section and click the Rightwards arrow icon to move 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, and stored procedures to the destination database.
      Rename Databases and Tables
      • To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section.
      • To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section.
      Note If you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be migrated.
      Filter data

      You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.

      Select the SQL operations to be migrated In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to migrate. For more information, see SQL operations that can be migrated.
    • Advanced SettingsAdvanced Settings
      Parameter Description
      Set Alerts
      Specify whether to set alerts for the data migration task. If the task fails or the migration latency exceeds the threshold, the alert contacts will receive notifications.
      • Select No if you do not want to set alerts.
      • Select Yes to set alerts. In this case, you must also set the alert threshold and alert contacts.
      Capitalization of Object Names in Destination Instance

      Specify 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 make sure that the capitalization of object names is consistent with that of the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.

      Replicate Temporary Tables When DMS Performs DDL Operations
      If you use Data Management (DMS) to perform online DDL operations on the source database, you can specify whether to migrate temporary tables generated by online DDL operations.
      • Yes: DTS migrates the data of temporary tables generated by online DDL operations.
        Note If online DDL operations generate a large amount of data, the migration task may be delayed.
      • No: DTS does not migrate the data of temporary tables generated by online DDL operations. Only the original DDL data of the source database is migrated.
        Note If you select No, the tables in the destination database may be locked.
      Retry Time for Failed Connections
      Specify the retry time for failed connections. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the retry time to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time, DTS resumes the data migration task. Otherwise, the data migration task fails.
      Note
      • If multiple DTS instances have the same source or destination database, the lowest value takes effect. For example, the retry time is set to 30 minutes for Instance A and 60 minutes for Instance B, DTS retries failed connections at an interval of 30 minutes.
      • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time based on your business needs. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
  6. Specify the primary key column and distribution key of the table that you want to migrate to the AnalyticDB for MySQL cluster.
    AnalyticDB for MySQL: Specify the primary key column and distribution key
    Note If you select Schema Migration as the migration type, you must specify the type, primary key column, and distribution key for the tables that you want to migrate to the AnalyticDB for MySQL V3.0 cluster. For more information, see CREATE TABLE.
  7. In the lower part of the page, click Next: Precheck and Start Task.
    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, you can click the Info icon icon next to each failed item to view details.
      • You can troubleshoot the issues based on the causes and run a precheck again.
      • If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
  8. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
  9. On the Purchase Instance page, specify the Instance Class parameter for the data migration instance. The following table describes the parameter.
    Section Parameter Description
    Parameters Instance Class

    DTS provides several instance classes that have different performance in migration speed. You can select an instance class based on your business scenario. For more information, see Specifications of data migration instances.

  10. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
  11. Click Buy and Start to start the data migration task. You can view the progress of the task in the task list.