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Data Migration Overview

Last updated: 2022-09-21 17:24:21

    Feature Overview

    The data migration feature refers to data replication between different data sources. It is a short-term one-time task that migrates the entire database. After migration, cutover will be performed to continue the task in the new database. DTS supports non-stop data migration without locks to minimize the impact of database downtime on the business.

    DTS supports migration of self-built, TencentDB, and third-party cloud source databases.

    • Self-built database migration to the cloud: This means to migrate data from a self-built database based on a local IDC, CVM instance, or Lighthouse instance to TencentDB.
    • Cross-TencentDB instance migration: This includes database version upgrade, cross-region migration (including cross-border migration), and cross-account instance migration.
    • Third-party database migration: This means to migrate data from a database in another cloud such as Alibaba Cloud or AWS to Tencent Cloud.

    How It Works

    The following takes MySQL as an example to describe the data migration process:

    • Source database export: All existing data in the source database is exported.
    • Data import: Existing data is imported into the target database.
    • Incremental data sync and data check: Binlog takeover will begin when a migration task is started. During migration, SQL operations in the source database are written to the binlog, which DTS parses to write incremental data generated during existing data migration into the target database.

    Typical Use Cases

    Data migration to Tencent Cloud

    It simply takes a few steps in DTS to set up data migration to Tencent Cloud without any complicated configuration. The migration process does not interrupt the service provided by your source database, thereby minimizing the impact of cloudification on your business.

    Restrictions

    • Only basic tables and views can be migrated, and objects such as functions, triggers, and stored procedures are not supported currently (such unsupported migration objects will be gradually supported in the future).
    • Correlated data objects must be migrated together; otherwise, migration will fail. Common correlations include table reference by views, view reference by views, view/table reference by stored procedures/functions/triggers, and tables correlated through primary/foreign keys.

    Supported Migration Types

    DTS supports the following three migration types:

    • Structural migration: The structure of the migration objects in the source database is migrated to the target database.
    • Full migration: All data except system tables in the source database is migrated to the target database at a time. Full migration is one-time migration and is applicable to scenarios where the source database has no data writes.
    • Full + incremental migration: Full migration is performed first to initialize the target database, and then the incremental data is migrated. Technical methods such as log parsing are used to keep the data between the source and target databases consistent. Full + incremental migration is applicable to scenarios where the source instance has data writes.
    • If you select full data migration, do not write new data into the source instance during migration; otherwise, the data in the source and target instances will be inconsistent. In scenarios with data writes, to ensure the data consistency in real time, we recommend you select full + incremental migration.

    Supported Database Types

    For more information on the source and target database types, versions, and migration types supported for data migration, see Databases Supported by Data Migration.

    Supported Advanced Features

    Feature Description Documentation
    Heterogeneous migration and migration from third-party cloud databases Data migration between databases in different types is supported, such as migration from MySQL to TDSQL-C. Currently supported third-party cloud databases include Alibaba Cloud and AWS databases. Databases Supported by Data Migration
    Cross-account migration Data migration between different Tencent Cloud accounts is supported. Cross-Account TencentDB Instance Migration
    Cross-version migration of most databases The target database version should be equal to or later than the source database version; for example, data on v5.5.x can be migrated to v5.5.x, v5.6.x, or later. The last digit in the version number is the minor version number, which is not restricted. Databases Supported by Data Migration
    Migration of user information, views, and advanced objects User information, views, stored procedures, functions, triggers, and events can be migrated. -
    Data consistency check The data in the source and target databases can be checked for consistency. Creating Data Consistency Check Task
    Task progress visualization Information such as migration steps and progress can be displayed. Viewing Task
    Metric monitoring and default alarm policy
  • Data migration metrics can be monitored.
  • Default configuration is supported for data migration event monitoring to automatically notify you of abnormal events.
  • Supported Events and Metrics
    Migration without locks Migration is implemented without locks, during which no global lock (the FTWRL lock) is added, and only tables without a primary key are locked. -
    Database/Table mapping Databases/Tables migrated from the source database to the target database can be renamed. Renaming Database/Table
    Instance restart or upgrade During incremental migration, the instances can be restarted or upgraded. -
    HA switch HA switch from the source instance (with GTID enabled) to the target instance is supported. -
    No requirements for the super privileges The operator does not need to have the super privileges of the source instance account (only for certain databases currently). -
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