Updated on 2024-03-28 GMT+08:00

From MySQL to DDM

Supported Source and Destination Databases

Table 1 Supported databases

Source DB

Destination DB

  • On-premises databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • ECS databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • Other cloud databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • RDS for MySQL (5.5, 5.6, 5.7, 8.0)
  • DDM instances

Database Account Permission Requirements

To start a migration task, the source and destination database users must have permissions listed in the following table. Different types of migration tasks require different permissions. For details, see Table 2. DRS automatically checks the database account permissions in the pre-check phase and provides handling suggestions.

Table 2 Database account permission

Type

Full Migration

Full+Incremental Migration

Source database user

The user must have the following minimum permissions:

SELECT, SHOW VIEW, and EVENT

The user must have the following minimum permissions:

SELECT, SHOW VIEW, EVENT, LOCK TABLES, REPLICATION SLAVE, and REPLICATION CLIENT

Destination database user

  • The DDM destination database user must have the following permissions: CREATE, DROP, ALTER, INDEX, INSERT, DELETE, UPDATE, and SELECT. In addition, grant the SELECT permission on all tables.
  • The DDM destination database user must have the permission on the database to be migrated.
  • You are advised to create an independent database account for DRS task connection to prevent task failures caused by database account password modification.
  • After changing the account passwords for the source and destination databases, modify the connection information in the DRS task as soon as possible to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.

Supported Migration Objects

Different types of migration tasks support different migration objects. For details, see Table 3. DRS will automatically check the objects you selected before the migration.

Table 3 Migration objects

Type

Precautions

Migration objects

  • You can select table-level migration.
  • Only the source database data can be migrated. The table structure and other database objects of the source database cannot be migrated.
  • Only MyISAM and InnoDB tables can be migrated.
  • The system database and event statuses cannot be migrated.
  • Tables without primary keys cannot be migrated.
  • If the source database is MySQL 8.0, tables with function indexes cannot be migrated.
  • Full and incremental migrations do not support invisible columns. Invisible columns can be migrated since MySQL 8.0.23. For example:
    CREATE TABLE `test11` (
      `id` int NOT NULL,
      `c1` int DEFAULT NULL /*!80023 INVISIBLE */,
      PRIMARY KEY (`id`));

Precautions

To ensure tasks can run normally, DRS provides automatic pre-check. Before starting a DRS task, DRS checks the configurations and conditions of the source and destination databases. For details about the main check items and handling suggestions, see DRS Pre-Check Items. In addition to the pre-check items, you need to pay attention to the items listed in Table 4.

Table 4 Precautions

Type

Restrictions

Restrictions on the source database

  • If the source database is an on-premises database and has Percona Server for MySQL 5.6.x or Percona Server for MySQL 5.7.x installed, the memory manager must use Jemalloc to prevent Out of Memory errors caused by frequent queries on system tables.
  • The source database does not support the mysql binlog dump command.
  • The source database does not support the reset master or reset master to command, which may cause DRS task failures or data inconsistency.
  • Associated objects must be migrated at the same time to avoid migration failure caused by missing associated objects.
  • Cascade operations cannot be performed on tables with foreign keys. If the foreign key index of a table is a common index, the table structure may fail to be created. You are advised to use a unique index.
  • Due to the MySQL constraints, if the one-time event triggering time of the source database is earlier than the migration start time, the event will not be migrated to the destination database.

Use Restrictions

General

  • During the migration, do not modify or delete the usernames, passwords, and permissions of the source and destination databases or change the ports of the source and destination databases.
  • During migration, do not modify the destination database (including but not limited to DDL and DML operations) that is being migrated.
  • During migration, do not write the statement-based binlog into the source database.
  • During migration, do not clear the binlog in the source database.
  • During migration, do not create a database named ib_logfile in the source database.

Full migration

  • During task startup and full migration, do not perform DDL operations on the source database. Otherwise, the task may be abnormal.

Incremental migration

  • During an incremental migration of table-level objects, renaming tables is not supported.
  • During an incremental migration, do not perform the point-in-time recovery (PITR) operation on the source database.
  • During an incremental migration, resumable upload is supported. However, data may be repeatedly inserted into a non-transactional table that does not have a primary key when the server system breaks down.
  • During an incremental migration, the following DDL statements are supported: ADD COLUMN, MODIFY COLUMN, CHANGE COLUMN, CREATE INDEX, DROP INDEX, RENAME INDEX and ADD INDEX.

Stopping a task

  • If the destination DDM version is later than 3.0.4.1, DRS automatically updates the start value of the DDM sequence when the task is complete.

Other restrictions

  • If the DCC does not support instances with 4 vCPUs and 8 GB memory or higher instance specifications, the migration task cannot be created.
  • When creating multiple migration tasks in the many-to-one scenario, ensure that the read and write settings of the destination database are consistent in these tasks.
  • The table without a primary key lacks a unique identifier for rows. When the network is unstable, you may need to retry the task several times, or data inconsistency may occur.
  • If a physically generated column in a table is generated based on a time type, the data in the column may be inconsistent.
  • If the source and destination DB instances are RDS for MySQL instances, tables encrypted using Transparent Data Encryption (TDE) cannot be synchronized.
  • If the source MySQL database does not support TLS 1.2 or is a self-built database of an earlier version (earlier than 5.6.46 or between 5.7.0 and 5.7.28), you need to submit an O&M application for testing the SSL connection.
  • Before creating a DRS task, if concurrency control rules of SQL statements are configured for the source database, the DRS task may fail.
  • Ensure that the destination database is empty before starting the migration. Otherwise, data in the destination may be overwritten during incremental migration.
  • If the destination DB instance uses columns of the TIMESTAMP or DATETIME data type as its sharding key, the seconds precision of the column is removed after the migration.

Prerequisites

Procedure

  1. On the Online Migration Management page, click Create Migration Task.
  2. On the Create Replication Instance page, select a region and project, specify the task name, description, and the replication instance details, and click Create Now.

    • Task information description
      Figure 1 Migration task information
      Table 5 Task information

      Parameter

      Description

      Region

      The region where the replication instance is deployed. You can change the region. To reduce latency and improve access speed, select the region closest to your services.

      Project

      The project corresponds to the current region and can be changed.

      Task Name

      The task name must start with a letter and consist of 4 to 50 characters. It can contain only letters, digits, hyphens (-), and underscores (_).

      Description

      The description consists of a maximum of 256 characters and cannot contain special characters !=<>'&"\

    • Replication instance information
      Figure 2 Replication instance information

      Table 6 Replication instance settings

      Parameter

      Description

      Data Flow

      Select To the cloud.

      The destination is a DB instance on the current cloud.

      Source DB Engine

      Select MySQL.

      Destination DB Engine

      Select DDM.

      Network Type

      Available options: VPC, Public network, and VPN or Direct Connect. By default, the value is Public network.

      • VPC is suitable for migrations between cloud databases of the same account in the same region.
      • VPN or Direct Connect is suitable for migrations from on-premises databases to cloud databases or between cloud databases across regions.
      • Public network is suitable for migration from on-premises databases or external cloud databases to destination databases.

      Destination DB Instance

      The DDM instance you created.

      Replication Instance Subnet

      The subnet where the replication instance resides. You can also click View Subnet to go to the network console to view the subnet where the instance resides.

      By default, the DRS instance and the destination DB instance are in the same subnet. You need to select the subnet where the DRS instance resides, and there are available IP addresses for the subnet. To ensure that the replication instance is successfully created, only subnets with DHCP enabled are displayed.

      Migration Type

      • Full: This migration type is suitable for scenarios where service interruption is acceptable. All objects in non-system databases are migrated to the destination database at one time, including tables, views, stored procedures, and triggers.
        NOTE:

        If you are performing a full migration, do not perform operations on the source database. Otherwise, data generated in the source database during the migration will not be synchronized to the destination database.

      • Full+Incremental: This migration type allows you to migrate data without interrupting services. After a full migration initializes the destination database, an incremental migration initiates and parses logs to ensure data consistency between the source and destination databases.
        NOTE:

        If you select Full+Incremental, data generated during the full migration will be continuously synchronized to the destination database, and the source remains accessible.

    • AZ
      Figure 3 AZ
      Table 7 Task AZ

      Parameter

      Description

      AZ

      Select the AZ where you want to create the DRS task. Selecting the one housing the source or destination database can provide better performance.

    • Enterprise Project and Tags
      Figure 4 Enterprise projects and tags
      Table 8 Enterprise Project and Tags

      Parameter

      Description

      Enterprise Project

      An enterprise project you would like to use to centrally manage your cloud resources and members. Select an enterprise project from the drop-down list. The default project is default.

      For more information about enterprise projects, see Enterprise Management User Guide.

      To customize an enterprise project, click Enterprise in the upper right corner of the console. The Enterprise Project Management Service page is displayed. For details, see Creating an Enterprise Project in Enterprise Management User Guide.

      Tags

      • Tags a task. This configuration is optional. Adding tags helps you better identify and manage your tasks. Each task can have up to 20 tags.
      • If your organization has configured tag policies for DRS, add tags to tasks based on the policies. If a tag does not comply with the policies, task creation may fail. Contact your organization administrator to learn more about tag policies.
      • After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.

    If a task fails to be created, DRS retains the task for three days by default. After three days, the task automatically stops.

  3. On the Configure Source and Destination Databases page, wait until the replication instance is created. Then, specify source and destination database information and click Test Connection for both the source and destination databases to check whether they have been connected to the replication instance. After the connection tests are successful, select the check box before the agreement and click Next.

    • Source database configuration
      Figure 5 Source database information
      Table 9 Source database settings

      Parameter

      Description

      IP Address or Domain Name

      The IP address or domain name of the source database.

      Port

      The port of the source database. Range: 1 – 65535

      Database Username

      The username for accessing the source database.

      Database Password

      The password for the database username.

      SSL Connection

      SSL encrypts the connections between the source and destination databases. If SSL is enabled, upload the SSL CA root certificate.

      NOTE:
      • The maximum size of a single certificate file that can be uploaded is 500 KB.
      • If SSL is disabled, your data may be at risk.

      The IP address, domain name, username, and password of the source database are encrypted and stored in DRS, and will be cleared after the task is deleted.

    • Destination database configuration
      Figure 6 Destination database information
      Table 10 Destination database settings

      Parameter

      Description

      DB Instance Name

      The DDM instance selected when you create the migration task. This parameter cannot be changed.

      Database Username

      The username for accessing the destination DDM database.

      Database Password

      The password for the database username.

      The username and password of the destination database are encrypted and stored in DRS, and will be cleared after the task is deleted.

  4. On the Set Task page, select migration objects and click Next.

    Figure 7 Migration object
    Table 11 Migration object

    Parameter

    Description

    Migrate Object

    The left pane displays the source database objects, and the right pane displays the selected objects. You can migrate table-level objects to the destination database based on service requirements.

    If the source database is changed, click in the upper right corner before selecting migration objects to ensure that the objects to be selected are from the changed source database.

    NOTE:
    • If the object name contains spaces, the spaces before and after the object name are not displayed. If there are multiple spaces between the object name and the object name, only one space is displayed.
    • The name of the selected migration object cannot contain spaces.
    • To quickly select the desired database objects, you can use the search function.

  5. On the Check Task page, check the migration task.

    • If any check fails, review the cause and rectify the fault. After the fault is rectified, click Check Again.

      For details about how to handle check failures, see Solutions to Failed Check Items in Data Replication Service User Guide.

      Figure 8 Task Check
    • If the check is complete and the check success rate is 100%, click Next.

      You can proceed to the next step only when all checks are successful. If there are any items that require confirmation, view and confirm the details first before proceeding to the next step.

  6. On the displayed page, specify Start Time, Send Notifications, SMN Topic, Delay Threshold (s), and Stop Abnormal Tasks After and confirm that the configured information is correct and click Submit to submit the task.

    Figure 9 Task startup settings
    Table 12 Task startup settings

    Parameter

    Description

    Start Time

    Set Start Time to Start upon task creation or Start at a specified time based on site requirements. The Start at a specified time option is recommended.

    NOTE:

    The migration task may affect the performance of the source and destination databases. You are advised to start the task in off-peak hours and reserve two to three days for data verification.

    Send Notifications

    This parameter is optional. After enabled, select a SMN topic. If the status, latency metric, or data of the migration task is abnormal, DRS will send a notification.

    SMN Topic

    This parameter is available only after you enable Send Notifications and create a topic on the SMN console and add a subscriber.

    For details, see Simple Message Notification User Guide.

    Delay Threshold (s)

    During an incremental migration, a synchronization delay indicates a time difference (in seconds) of synchronization between the source and destination database.

    If the synchronization delay exceeds the threshold you specify, DRS will send alarms to the specified recipients. The value ranges from 0 to 3,600. To avoid repeated alarms caused by the fluctuation of delay, an alarm is sent only after the delay has exceeded the threshold for six minutes.

    NOTE:
    • In the early stages of an incremental migration, there is more delay because more data is waiting to be synchronized. In this situation, no notifications will be sent.
    • Before setting the delay threshold, enable Send Notifications.
    • If the delay threshold is set to 0, no notifications will be sent to the recipient.

    Data Exception Notification

    This parameter is optional. After enabled, DRS will send a notification if the task data is abnormal.

    Stop Abnormal Tasks After

    Number of days after which an abnormal task is automatically stopped. The value must range from 14 to 100. The default value is 14.

    NOTE:

    Tasks in the abnormal state are still charged. If tasks remain in the abnormal state for a long time, they cannot be resumed. Abnormal tasks run longer than the period you set (unit: day) will automatically stop to avoid unnecessary fees.

  7. After the task is submitted, view and manage it on the Online Migration Management page.

    • You can view the task status. For more information about task status, see Task Statuses.
    • You can click in the upper right corner to view the latest task status.
    • By default, DRS retains a task in the Configuration state for three days. After three days, DRS automatically deletes background resources, but the task status remains unchanged. When you reconfigure the task, DRS applies for resources again.