Updated on 2024-11-30 GMT+08:00

From MySQL to MySQL

Supported Source and Destination Databases

Table 1 Supported databases

Source DB

Destination DB

  • RDS for MySQL (5.5, 5.6, 5.7, 8.0)
  • 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)
    NOTE:

    The destination database version must be the same as or later than the source database version.

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

If the source database version is 8.0, the user must have the SELECT permission for the mysql.user table. If the source database version is 5.7 or earlier, the user must have the SELECT permission for the MySQL system database.

The user must have the following minimum permissions:

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

If the source database version is 8.0, the user must have the SELECT permission for the mysql.user table. If the source database version is 5.7 or earlier, the user must have the SELECT permission for the MySQL system database.

Destination database user

The user must have the following minimum permissions:

SELECT, CREATE, ALTER, DROP, DELETE, INSERT, UPDATE, INDEX, EVENT, CREATE VIEW, CREATE ROUTINE, TRIGGER, REFERENCES, and WITH GRANT OPTION. If the destination database version is in the range 8.0.14 to 8.0.18, the SESSION_VARIABLES_ADMIN permission is required.

To migrate data, you must have the SELECT, INSERT, UPDATE, and DELETE permissions for the MySQL database.

  • 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 of the DRS task by referring to Modifying Connection Information to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.
  • Table 2 lists the minimum permissions required by a DRS task. If you need to migrate the grant permission through a DRS task, ensure that the connection account of the DRS task has the corresponding permission. Otherwise, the destination database user may not be authorized due to grant execution failure. For example, if the connection account of the DRS task does not require the process permission, but you need to migrate the process permission through a DRS task, ensure that the connection account of the DRS task has the process permission.

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

  • The source database names cannot contain non-ASCII characters, or the following characters: .'<`>/\"
  • The source table and view names cannot contain non-ASCII characters, or the following characters: '<>/\"
  • You can select table-, database-, or instance-level (all-level) migration.
  • Databases, tables, users, views, indexes, constraints, functions, stored procedures, triggers, and events can be migrated.
  • Only MyISAM and InnoDB tables can be migrated.
  • The system database and event statuses cannot be migrated.
  • Non-standard floating-point data that can be written in loose mode but cannot be written in strict mode cannot be migrated. Such non-standard floating-point data may fail to be hit, causing data migration failures.
  • 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

  • The source database names cannot contain non-ASCII characters, or the following characters: .'<`>/\"
  • The source table and view names cannot contain non-ASCII characters, or the following characters: '<>/\"
  • The column names in the source database tables cannot end with a backslash (\).
  • 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.

Restrictions on usage

General

  • During the migration, you are not advised to 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.
  • During the migration, 0 cannot be written to the auto-increment primary key column in the source database. Otherwise, the data of the auto-increment column in the source database is inconsistent with that in the destination database.
  • During the migration, do not upgrade the source MySQL database across major versions. Otherwise, data may become inconsistent or the migration task may fail (data, table structures, and keywords may cause compatibility changes after the cross-version upgrade). You are advised to create a migration task again if the source MySQL database is upgraded across major versions.
  • If index migration is required for a DRS task, the destination database table cannot contain indexes with the same name but different columns. In the full phase, DRS ignores the existing indexes with the same name. In the incremental phase, DDL operations on indexes based on the index name trigger misplacement.

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.
  • DDL statements are supported in the incremental migration phase.

Stopping a task

  • Stop a task normally.

    The selected events and triggers are migrated while the migration task proceeds to the final stage. Before a task is completed, ensure that the source and destination databases are connected and pay attention to the migration status reported by the migration log.

  • Forcibly stop a task.

    If you forcibly stop a task, DRS resources will be released and triggers and events will not be migrated. You need to manually migrate triggers and events. If you want DRS to migrate triggers and events, restore the DRS task first. After the task status becomes normal, stop the task.

Troubleshooting

  • If any problem occurs during task creation, startup, full synchronization, incremental synchronization, or completion, rectify the fault by referring to Troubleshooting.

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.
  • If the source and destination database versions are different, syntax compatibility issues may occur due to feature differences between the source and destination database versions. For details, see Syntax Differences Between MySQL Versions.
  • 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.
  • The destination database cannot be restored to a point in time when a full migration was being performed.
  • If Transparent Data Encryption (TDE) is enabled for the source database table, TDE must also be enabled for the destination database. Otherwise, the table structure fails to be created and the task will be abnormal. You can create an unencrypted table structure in the destination database to avoid this problem.
  • If the destination 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.
  • If the destination database version is 5.7, the last digit 0 after the decimal point is lost in the floating point number of the JSON type due to version restrictions. The value comparison result will be inconsistent due to precision loss.
  • During the full and incremental migration phases, 0 cannot be written to the auto-increment primary key column in the source database. Otherwise, the data of the auto-increment column in the source database is inconsistent with that in the destination database.
  • Before creating a DRS task, if concurrency control rules of SQL statements are configured for the source or destination database, the DRS task may fail.

Prerequisites

Procedure

This section uses the migration from an RDS for MySQL database to a MySQL database on an ECS as an example to describe how to configure a migration task in a VPC network on the DRS management console.

  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 Out of the cloud.

      The source database is a database on the current cloud.

      Source DB Engine

      Select MySQL.

      Destination DB Engine

      Select MySQL.

      Network Type

      Available options: Public network, VPC, VPN or Direct Connect

      • 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 migrations from on-premises databases or external cloud databases to destination databases.

      Source DB Instance

      Select the DB instance whose data is to be migrated out of the cloud.

      Replication Instance Subnet

      The subnet where the replication instance resides. You can also click View Subnets 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 and data in non-system databases are migrated to the destination database at one time. The objects include tables, views, and stored procedures.
        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.

      Specify EIP

      This parameter is available when you select Public network for Network Type. Select an EIP to be bound to the DRS instance. DRS will automatically bind the specified EIP to the DRS instance and unbind the EIP after the task is complete. The number of specified EIPs must be the consistent with that of DB instances.

      For details about the data transfer fee generated using a public network, see EIP Price Calculator.

    • 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, configure your own DNS server, 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.

    • (Optional) Configuring your own DNS server
      Figure 5 DNS Server
      Table 9 DNS server information

      Parameter

      Description

      DNS Server

      Enable this option if you need to use the IP address of your own DNS server as the source or destination database IP address.

      DNS Server IP Address

      Add the IP address of your own DNS server to DNS Server IP Address.

      Then, you can also enter this IP address in IP Address or Domain Name in the Source Database or Destination Database area for data migration.

      This function is available when you need to use the IP address of your own DNS server as the source or destination database IP address.

      Only whitelisted users can use this function. You need to submit a service ticket to apply for this function. In the upper right corner of the management console, choose Service Tickets > Create Service Ticket to submit a service ticket.

    • Source database information
      Figure 6 Source database information
      Table 10 Source database settings

      Parameter

      Description

      DB Instance Name

      The RDS DB instance selected during migration task creation. This parameter cannot be changed.

      Database Username

      Enter the username of the source database.

      Database Password

      The password for the database username.

      If the task is in the Starting, Full migration, Incremental migration, or Incremental migration failed status, in the Connection Information area on the Basic Information tab, click Modify Connection Details. In the displayed dialog box, change the password.

      SSL Connection

      If SSL connection is required, enable SSL on the source database, ensure that related parameters have been correctly configured, and upload an SSL 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 username and password of the source database are encrypted and stored in the database and the replication instance during the migration. After the task is deleted, the username and password are permanently deleted.

    • Destination database information
      Figure 7 Destination database information
      Table 11 Destination database settings

      Parameter

      Description

      VPC

      A dedicated virtual network in which the destination database is located. It isolates networks for different services.

      Subnet

      A subnet provides dedicated network resources that are isolated from other networks, improving network security. The subnet must be in the AZ where the source database resides. You need to enable DHCP for creating the source database subnet.

      IP Address or Domain Name

      Enter the IP address or domain name of the destination database.

      Port

      The port of the destination database. Range: 1 - 65535

      Database Username

      The username for accessing the destination database.

      Database Password

      The password for the database username. You can change the password if necessary. To change the password, perform the following operation after the task is created:

      If the task is in the Starting, Full migration, Incremental migration, or Incremental migration failed status, in the Connection Information area on the Basic Information tab, click Modify Connection Details. In the displayed dialog box, change the password.

      SSL Connection

      If SSL connection is required, enable SSL on the destination database, ensure that related parameters have been correctly configured, and upload an SSL 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.

      Migrate Definer to User

      Indicates whether to migrate the Definers of all source database objects to the destination database user entered during the connection test.

      • Yes

        The Definers of all source database objects will be migrated to the user. Other users do not have permissions for database objects unless these users are authorized. For details about authorization, see How Do I Maintain the Original Service User Permission System After Definer Is Forcibly Converted During MySQL Migration?

        For example, if the view is CREATE ALGORITHM=UNDEFINED DEFINER=`username`@`%` SQL SECURITY DEFINER VIEW `test_db`.`view5` AS select 1 AS `1` before migration,

        it is converted to CREATE ALGORITHM=UNDEFINED DEFINER=`drsUser`@`%` SQL SECURITY DEFINER VIEW `test_db`.`view5` AS select 1 AS `1` after the migration.

        drsUser indicates the destination database user used for testing the connection.

      • No

        The Definers of all source database objects will not be changed. You need to migrate all accounts and permissions of the source database in the next step. Note that if the Definer account is not found in the destination database, unavailable objects will be created.

        For details about Definer, see the MySQL official document.

      The IP address, port, username, and password of the destination database are encrypted and stored in the database and the replication instance, and will be cleared after the task is deleted.

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

    Figure 8 Migration Type

    Table 12 Migration types and objects

    Parameter

    Description

    Flow Control

    You can choose whether to control the flow. Flow Control takes effect in the full phase only.

    • Yes

      You can customize the maximum migration speed. During the migration, the migration speed of each task (or each subtask in multi-task mode) does not exceed the value of this parameter.

      In addition, you can set the time range based on your service requirements. The traffic rate setting usually includes setting of a rate limiting time period and a traffic rate value. Flow can be controlled all day or during specific time ranges. The default value is Always. A maximum of 10 time ranges can be set, and they cannot overlap.

      The flow rate must be set based on the service scenario and cannot exceed 9,999 MB/s.

      Figure 9 Configuring flow control

    • No
      The migration speed is not limited and the outbound bandwidth of the source database is maximally used, which will increase the read burden on the source database. For example, if the outbound bandwidth of the source database is 100 MB/s and 80% bandwidth is used, the I/O consumption on the source database is 80 MB/s.
      NOTE:
      • Flow control mode takes effect only during a full migration.
      • You can also change the flow control mode after creating a task. For details, see Modifying the Flow Control Mode.

    Migrate Incremental Accounts and Permissions

    Indicates whether to migrate incremental accounts and permissions during database migration.
    • Yes

      All incremental accounts and permissions will be migrated. The migration of incremental accounts and permissions may fail because the source and destination database versions and account encryption modes may be different.

    • No

      All incremental accounts and permissions will be filtered out during the migration.

    Filter DROP DATABASE

    During an incremental migration, executing DDL operations on the source database may affect the data migration performance to some extent. To reduce data migration risks, DRS allows you to filter out DDL operations.

    The database deletion operation can be filtered out by default.

    • If you select Yes, any database deletion operations performed on the source database are not synchronized during data migration.
    • If you select No, related operations are synchronized to the destination database during data migration.

    Migrate Account

    During a database migration, accounts need to be migrated separately.

    There are accounts that can be migrated completely, accounts whose permissions need to be reduced, and accounts that cannot be migrated. You can choose whether to migrate the accounts based on service requirements. If you select Yes, you can select the accounts to be migrated as required.
    • No

      During the migration, accounts, permissions, and passwords are not migrated.

    Create Indexes Along With Table Structure

    Indicates whether to create indexes along with the table structure in the full migration phase.

    • Yes: Indexes are migrated when the table structure is migrated in the full migration phase.
    • No: Indexes are migrated separately after data migration.

    Migrate Object

    The left pane displays the source database objects, and the right pane displays the selected objects. You can choose to migrate all objects, tables, or databases based on your service requirements.

    • All: All objects in the source database are migrated to the destination database. After the migration, the object names will remain the same as those in the source database and cannot be modified.
    • Tables: The selected table-level objects will be migrated.
    • Databases: The selected database-level objects will be migrated.

    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 you choose not to migrate all of the databases, the migration may fail because the objects, such as stored procedures and views, in the databases to be migrated may have dependencies on other objects that are not migrated. To prevent migration failure, migrate all of the databases.
    • If an object name contains spaces, the spaces before and after the object name are not displayed. If there are two or more consecutive spaces in the middle of 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.

    • 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 10 Task startup settings

    Table 13 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 task billing is about to start, the status, latency metric, or data of the migration task is abnormal, DRS will send you 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.
    • After the full migration is complete, you can use data comparison to check whether the data is consistent before and after the migration.
    • 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.
    • For a public network task, DRS needs to delete background resources after you stop the task. The EIP bound to the task cannot be restored to the Unbound state until background resources are deleted.