Help Center/ Data Replication Service/ User Guide (Kuala Lumpur Region)/ Real-Time Synchronization/ To the Cloud/ From MySQL to GaussDB(DWS)
Updated on 2025-08-07 GMT+08:00
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From MySQL to GaussDB(DWS)

Supported Source and Destination Databases

Table 1 Supported databases

Source DB

Destination DB
  • On-premises MySQL databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • ECS-hosted MySQL databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • Other cloud MySQL databases (MySQL 5.5, 5.6, 5.7, and 8.0)
  • RDS for MySQL (5.5, 5.6, 5.7, 8.0)
  • TaurusDB Standard Edition (5.7 and 8.0)

GaussDB(DWS) (versions 8.1.3 and 8.2.0)

This function is in restricted use.

Database Account Permission Requirements

To start a synchronization task, the source and destination database users must meet the requirements in the following table. Different types of synchronization 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, Incremental, and Full+Incremental

Source database user

The user must have the following minimum permissions:

SELECT, LOCK TABLES, REPLICATION SLAVE, and REPLICATION CLIENT

Destination database user

Each table in the destination database must have the INSERT, SELECT, UPDATE, DELETE, CONNECT and CREATE permissions.
  • 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.

Supported Synchronization Objects

Table 3 lists the objects that can be synchronized in different scenarios. DRS will automatically check the objects you selected before the synchronization.

Table 3 Supported synchronization objects

Type

Precautions

Synchronization objects
  • Tables, common indexes (B-Tree indexes), and constraints (primary key, empty, and not-null) can be synchronized.
  • MyISAM and InnoDB tables can be synchronized.
  • Comment is supported in full synchronization mode, but not supported in incremental synchronization mode.
  • Views, foreign keys, stored procedures, triggers, functions, events, virtual columns, unique constraints, and unique indexes cannot be synchronized.
  • A user-defined table that has no primary key and is a partitioned table cannot be synchronized..
  • Replication tables without primary keys of GaussDB(DWS) cannot be synchronized. If a table to be synchronized is a replication table without a primary key in GaussDB(DWS), the task will fail.
  • The column name of the synchronization object cannot be a field forbidden by GaussDB(DWS), such as CTID, XMIN, CMIN, XMAX, CMAX, TABLEOID, XC_NODE_ID and TID. Otherwise, the task fails.
  • Full and incremental synchronizations do not support invisible columns. Invisible columns can be synchronized 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 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 names of the source databases and tables cannot contain non-ASCII characters, or the following special characters: .<'>/\" Object names in the source database table cannot contain unclosed left braces ({). Object names involve table names, index names, partition names, and column names.
  • The column names in the source database tables cannot end with a backslash (\).
  • The source database does not support the reset master or reset master to command, which may cause DRS task failures or data inconsistency.
  • 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.

Restrictions on usage

General

  • If you change the port of the RDS source database and the synchronization task fails, retry the task.
  • During real-time synchronization, if the source is not RDS, the port cannot be changed.
  • During real-time synchronization, the IP address, account, and password cannot be changed.
  • Do not perform data restoration on the source database.
  • Binlogs cannot be forcibly cleared.
  • During data synchronization, do not upgrade the source MySQL database across major versions. Otherwise, data may become inconsistent or the synchronization task may fail (data, table structures, and keywords may cause compatibility changes after a cross-version upgrade). You are advised to create a synchronization task again if the source MySQL database is upgraded across major versions.
  • In MySQL 5.6 and earlier versions, garbled characters can be stored in data columns. These garbled characters cannot be queried, and data consistency cannot be guaranteed after synchronization.

Full synchronization

  • When a DRS task is being started or in the full synchronization phase, do not perform DDL operations on the source database. Otherwise, the task may be abnormal.

Incremental synchronization

  • If the session variable character_set_client is set to binary, some data may include garbled characters.
  • During an incremental synchronization, tables whose primary key type is binary, text, blob, or clob cannot be deleted or updated on the destination database.
  • Tables without primary keys created during database-level synchronization must contain one of the following.

    Integer types: TINYINT, SMALLINT, INT, BIGINT, and NUMERIC/DECIMAL

    Character types: CHAR, BPCHAR, VARCHAR, VARCHAR2, and NVARCHAR2

    Date/time types: DATE, TIME, TIMETZ, TIMESTAMP, TIMESTAMPTZ, INTERVAL, and SMALLDATETIME

    For a table without a primary key, a column that can be used as a distribution column is specified as the distribution column. If all column types cannot be used as distribution columns, the table fails to be created and DRS synchronization is interrupted.

  • During incremental synchronization, DDL operations (such as ALTER TABLE ddl_test ADD COLUMN c2 AFTER/FIRST c1) for adding columns to a specified position are not supported. DRS will delete the AFTER/FIRST attribute, which may cause column sequence inconsistency.
  • During incremental synchronization, executing non-idempotent DDL statements (for example, ALTER TABLE ddl_test ADD COLUMN c3 timestamp default now();) may cause data inconsistency.
  • During incremental synchronization, the following DDL operations are supported by default:
    • In one-to-one synchronization, the following DDL operations are synchronized by default: CREATE_TABLE, RENAME_TABLE, ADD_COLUMN, MODIFY_COLUMN, ALTER_COLUMN, DROP_CONSTRAINT, ADD_CONSTRAINT, CREATE_INDEX, DROP_INDEX, RENAME_INDEX, and RENAME_COLUMN. You can select the DDL operations to be synchronized on the object selection page as required.
    • If you rename a column in many-to-one synchronization, you must stop services. Otherwise, data inconsistency may occur.
    • In many-to-one scenarios, you are advised to synchronize ADD_COLUMN only. Other DDL synchronization may cause task failures or data inconsistency due to destination table changes.
    • In many-to-one scenarios, when running ADD_COLUMN, ensure that the types of columns added to each table are the same. Otherwise, the task may fail.
    • The name of a table, column, or index to be added or modified cannot exceed 63 characters. Otherwise, the task fails.
    • When an index is creating using a DDL statement, if the table name and index name in the statement contain more than 63 characters, duplicate names may occur. As a result, the index fails to be created.
    • If a primary key is added to a table that does not have a primary key in the source database, the DDL operation must contain the first column. Otherwise, the task fails.
    • When a DDL operation is performed in the incremental phase, if the destination table is not found, the DDL operation will be ignored.
    • In the incremental phase, if CHANGE COLUMN is performed in the source database to modify a column and the column is a distribution column in destination GaussDB(DWS), the statement will be ignored because GaussDB(DWS) does not support distribution column modification.
    • In the incremental phase, the RENAME INDEX operation is not supported because the index rules of the source and destination databases are different.
    • In the incremental phase, you are not advised to combine CHAR(0) with other characters for data synchronization. For example, inserting CONCAT('a',CHAR(0),'b') may cause data inconsistencies.
    • In the incremental phase, you are not advised to combine CHAR(34) (double quotation marks) and CHAR(92) (backslash) with other characters for JSON data synchronization. For example, inserting JSON_OBJECT('$.0', CONCAT('a', CHAR(34), 'b')) may cause data inconsistencies because an extra backslash (\) will be added after it is synchronized to the destination end.

Stopping a task

  • Stop a task normally.

    Before a task is completed, ensure that the source and destination databases are connected and pay attention to the synchronization status reported by the synchronization log.

  • Forcibly stop a task.

    If you forcibly stop a task, DRS resources will be released.

Other restrictions
  • Associated objects must be synchronized at the same time to avoid synchronization failure due to missing associated objects. Common association: Indexes reference tables.
  • The source database cannot be restored.
  • Binlogs cannot be forcibly deleted. Otherwise, the synchronization task fails.
  • If there is a unique key when a table without a primary key is synchronized, data may fail to be written due to data conflicts.
  • Do not use an imprecise value type as the primary key in the database. This feature affects the synchronization of UPDATE and DELETE statements in the DRS incremental scenario.
  • If tables without primary keys contain large fields (BLOB, TEXT, CLOB, NCLOB, or BYTEA), data of the large fields may be inconsistent during incremental synchronization.
  • If the source is an RDS for MySQL instance and the destination is a GaussDB(DWS) instance, multiple source tables can be mapped to one destination table. For details, see From MySQL to GaussDB(DWS).
  • Before creating a DRS task, if concurrency control rules of SQL statements are configured for the source database, the DRS task may fail.
  • MySQL 5.7 filters CHECK constraints. If the source database version is 5.7, you are not advised to use CHECK constraints, which may cause data inconsistencies.
  • If the network is reconnected within 30 seconds, real-time synchronization will not be affected. If the network is interrupted for more than 30 seconds, the synchronization task will fail.
  • After being synchronized to the destination GaussDB(DWS) database, the unique key of the MySQL database is changed to a common constraint. The primary key remains unchanged.
  • The destination table can contain more columns than the source table. However, the following failures must be avoided:
    • Assume that extra columns on the destination database cannot be null or have default values. If newly inserted data records are synchronized from the source database to the destination database, the extra columns will become null, which does not meet the requirements of the destination database and will cause the task to fail.
    • Assume that extra columns on the destination database must be fixed at a default value and have a unique constraint. If newly inserted data records are synchronized from the source database to the destination database, the extra columns will contain multiple default values. That does not meet the unique constraint of the destination database and will cause the task to fail.
  • In MySQL, different tables in the same database (schema) can have the same index name or constraint name. In GaussDB(DWS), the index and constraint names are unique in the same schema, and the length is limited. To prevent conflicts between index and constraint names, the original index name in the table is changed to the following format after synchronization: hash value + original index name (which may be truncated) + _key. The hash value is calculated based on the original database name_original table name_original index name. Similarly, the original constraint name in the table is changed to the following format after synchronization: hash value + original constraint name (which may be truncated) + _key, or table name_original index name.
  • In the full synchronization phase, only B-Tree indexes are synchronized. Other indexes are not synchronized by default. If there are too many GaussDB(DWS) indexes, the storage space and data import performance will be affected. You are advised to create indexes based on service requirements.
  • In a full synchronization for the table structure, the length of char, varchar, nvarchar, enum, and set characters in the source database automatically increases by byte in the destination database (because the length of the destination database is in the unit of byte).
  • When the structure of a partitioned table is synchronized during a full synchronization, the partitioned table is converted to a non-partitioned table. During incremental synchronization, operations on partitioned tables in the source database may fail to be synchronized to the destination database or fail to be executed in the destination database. During incremental partition table synchronization, partition tables are created based on the types supported by GaussDB(DWS), which may fail.
  • When the timestamp data is to be synchronized in full synchronization, the on update current_timestamp syntax in the default value will not be synchronized to the destination GaussDB(DWS).
  • The DDL operation of renaming an unselected table is filtered out during the synchronization. As a result, the task may fail or data may be inconsistent.
    • If you rename table A to the name of table B and tables A and B are selected for synchronization, this RENAME statement will not be filtered out.
    • If you rename table A to the name of table B but table B is not synchronized, this RENAME statement will be filtered out.
    • You are not advised to perform the rename operation in the many-to-one synchronization scenario. Otherwise, the task may fail or data may be inconsistent.
  • The SQL statements in the DDL for incremental synchronization come from the native SQL statements executed by users. The table structure syntax for full synchronization is the SQL statements processed by the SQL syntax layer. The types or constraints of these SQL statements are different. As a result, the table structures or field types created in full synchronization and incremental synchronization may be different.
  • If the source table to be synchronized has the AUTO_INCREMENT attribute, DRS automatically updates the start value of the GaussDB auto-increment sequence corresponding to the integer sequence of the table when the task is complete. The updated value is the maximum value of the sequence plus 10,000.

Procedure

This section uses many-to-one synchronization from RDS for MySQL to GaussDB(DWS) as an example to describe how to configure a real-time synchronization task.

  1. On the Data Synchronization Management page, click Create Synchronization Task.
  2. On the Create Synchronization Instance page, specify the task name, description, and the synchronization instance details, and click Create Now.

    • Task information description
      Table 5 Task information

      Parameter

      Description

      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 !=<>'&"\
    • Synchronization instance information

      Table 6 Synchronization instance settings

      Parameter

      Description

      Data Flow

      Select To the cloud.

      Source DB Engine

      Select MySQL.

      Destination DB Engine

      Select GaussDB(DWS).

      Network Type

      The VPC network is used as an example. Available options: VPC, Public network and VPN or Direct Connect

      • VPC is suitable for data synchronization between cloud databases of the same account in the same region and VPC.
      • Public network is suitable for data synchronization from on-premises or external cloud databases to the destination databases bound with an EIP.
      • VPN or Direct Connect is suitable for data synchronization from on-premises databases to cloud databases, between databases of different accounts in the same region on the cloud, or between databases across regions on the cloud using a VPN, Direct Connect, Cloud Connect, VPCEP, or a VPC peering connection.

      Destination DB Instance

      An available GaussDB(DWS) instance.

      Synchronization Instance Subnet

      Select the subnet where the synchronization instance is located. 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 synchronization instance is successfully created, only subnets with DHCP enabled are displayed.

      IP Address Type

      The IP address type of the synchronization instance. IPv4 and IPv4/IPv6 dual stack are available.

      • IP Address Type can be set to IPv4/IPv6 dual stack only when IPv4/IPv6 dual stack is enabled for the selected VPC and subnet.
      • If you select IPv4/IPv6 dual stack and the source or destination database is connected by selecting an instance, DRS preferentially uses an IPv4 address to access the database.

      Synchronization Mode

      The synchronization mode supported by a DRS task. Full+Incremental is used as an example.

      • Full+Incremental

        This synchronization mode allows you to synchronize data in real time. After a full synchronization initializes the destination database, an incremental synchronization parses logs to ensure data consistency between the source and destination databases.

        NOTE:

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

      • Full

        All database objects and data you selected are synchronized to the destination database at a time. This mode is applicable to scenarios where service interruption is acceptable.

      • Incremental

        In this mode, incremental data generated on the source database is continuously synchronized to the destination database through log parsing.

      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.
    • Task Type
      Table 7 Task type information

      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.
    • Tags

      Table 8 Tags

      Parameter

      Description

      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 synchronization 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 synchronization instance. After the connection tests are successful, select the check box before the agreement and click Next.

    Table 9 Source database settings

    Parameter

    Description

    Database Type

    Select Self-built database or RDS DB instance.

    DB Instance Name

    Select the RDS DB instance to be synchronized.

    Database Username

    The username for accessing the source database.

    Database Password

    The password for the database username.

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

    Table 10 Destination database settings

    Parameter

    Description

    DB Instance Name

    The default value is the GaussDB(DWS) instance selected for creating the migration task. It cannot be changed.

    Database Username

    The username for accessing the destination database.

    Database Password

    The database username and password are encrypted and stored in the system and will be cleared after the task is deleted.

  4. On the Set Synchronization Task page, select the synchronization object type and synchronization object. Click Next.

    Table 11 Synchronization mode and object

    Parameter

    Description

    Flow Control

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

    • Yes

      You can set a maximum synchronization speed, which varies depending on network conditions. During the synchronization, the synchronization speed of each task (or each subtask in multi-task mode) will not exceed the threshold you configure.

      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.

    • No
      The synchronization 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:
      • The flow control mode takes effect only in the full synchronization phase.
      • You can also change the flow control mode after creating a task. For details, see Modifying the Flow Control Mode.

    Synchronization Object Type

    You can select Table structure, Data, or Index for Synchronization Object Type for full synchronization.

    • Data is selected by default.
    • If Table structure is selected, the destination database cannot contain tables whose names are the same as the source tables to be synchronized.
    • If Table structure is not selected, the destination database must have tables that match the source tables, and the table structure must be the same as the selected source table structures.

    The table structure of a GaussDB(DWS) database has service logic. You are advised to create a table structure under the guidance of GaussDB(DWS) experts based on service requirements and ensure that the table names, column names, and column types are correct. Otherwise, data synchronization may fail and data synchronization precision may be lost.

    Incremental Conflict Policy

    The conflict policy refers to the conflict handling policy during incremental synchronization. By default, conflicts in the full synchronization phase are ignored. Select any of the following conflict policies:

    • Ignore

      The system will skip the conflicting data and continue the subsequent synchronization process. If you select Ignore, data in the source database may be inconsistent with that in the destination database.

    • Report error

      The synchronization task will be stopped and fail.

    • Overwrite

      Conflicting data will be overwritten.

    Abnormal Data Policy

    Differences between the source and destination databases may cause some data to fail to be written. In this case, there may be abnormal data. Select this option based on how well abnormal data can be tolerated.

    • Continue: A small amount of abnormal data will not cause the synchronization of all data to be stopped. If there is abnormal data, dirty data is automatically recorded. You can view the dirty data in the abnormal data module.
    • Failed: If there is an exception during a task, the task fails and does not continue.

    Synchronize DML

    Select the DML operations to be synchronized. By default, all DML operations are selected.

    If you do not select Delete, DELETE statements in the incremental data of the source database will not be synchronized, which may cause a data inconsistency. As a result, there may be a data conflict or the task may fail.

    Start Point

    This option is available if you select Incremental in 2. The logs of the source database are obtained from the position after the start point during an incremental synchronization.

    Run show master status to obtain the start point of the source database and set File, Position, and Executed_Gtid_Set as prompted.

    Synchronize DDLs

    DDL type for incremental synchronization. You can select Default or Custom based on your service requirements.

    • Default
      • During database-level synchronization, all DDL operations in the binlog related to database objects, except DDL related to permissions, are synchronized to the destination. Common DDL statements are CREATE_TABLE and RENAME_TABLE.
      • During table-level synchronization, only DDL operations in the binlog related to the selected tables are synchronized. Common DDL statements are ADD_COLUMN, MODIFY_COLUMN, and ALTER_COLUMN.
    • Custom: You can select the DDL type to be synchronized as required. The DDL types supported by different data flow types are displayed on the GUI.

    Synchronization Object

    The left pane displays the source database objects, and the right pane displays the selected objects. You can select Tables or Databases for Synchronization Object as required.

    • If the synchronization objects in source and destination databases have different names, you can map the source object name to the destination one in the right pane. When selecting synchronization objects, you can also map multiple tables to one table. For details, see Changing Object Names (Mapping Object Names).
      • When you map multiple tables to one table, use the additional column to process data to avoid data conflicts.
      • The structure of the source database tables to be mapped must be the same as that of the destination database table.
    NOTE:
    • To quickly select the desired database objects, you can use the search function.
    • If there are changes made to the source databases or objects, click in the upper right corner to update the objects to be synchronized.
    • Object names will be converted to lowercase letters after being synchronized to the destination database. Therefore, the selected source database tables cannot contain tables with the same name but different letter cases. Otherwise, the synchronization fails.
    • 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 synchronization object cannot contain spaces.
    • In incremental synchronization at the database level, do not create tables with the same name but different letter cases in the source database. Otherwise, one of the tables cannot be synchronized.

  5. On the Processing Data page, filter data or add additional columns for the table object to be processed, and click Next.

    • If you need to set data filtering, click Data Filtering and set related filtering rules.
    • If you need to add additional columns, click the Additional Columns tab, click Add in the Operation column, and enter the column name and the operation type.

      For details about related operations, see Processing Data.

  6. On the Check Task page, check the synchronization task.

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

  7. On the displayed page, specify Start Time, confirm that the configured information is correct, and click Submit to submit the task.

    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.

    NOTE:

    After a synchronization task is started, the performance of the source and destination databases may be affected. You are advised to start a synchronization task during off-peak hours.

  8. After the task is submitted, you can view and manage it on the Data Synchronization 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 configure the task again, DRS applies for resources for the task again. In this case, the IP address of the DRS instance changes.
    • 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.

Parent topic: To the Cloud