Overview|V4.2.11|OceanBase Migration Service|docs|OceanBase Documentations

OceanBase Migration Service (OMS) Community Edition supports real-time data transmission between OceanBase Database Community Edition and different types of data sources, such as MySQL, TiDB, and PostgreSQL, and supports data migration between MySQL-compatible tenants of OceanBase Database Community Edition.

Background information

OMS Community Edition supports online migration. Before you start a data migration task, you must configure the source data source and the target data source to connect the server where OMS Community Edition is deployed to both the source and target instances, and select the migration objects.

OMS Community Edition automatically executes all steps of a data migration task to copy objects, existing data, or incremental data from the source database or table to the target database or table, and ensures real-time incremental synchronization from the source database to the target database.

Supported migration task types

OMS Community Edition supports the following migration task types:

Note

For more information about the version restrictions on data sources, see Limitations.

Supported migration types

The following table describes the migration types supported by OMS Community Edition. For more information about each migration type, see the topic about creating a data migration task between the corresponding types of data sources in the "Data Migration" chapter.

Migration type	Description
Schema migration	Migrates the definitions of data objects, such as tables, indexes, constraints, comments, and views, from the source database to the target database. Temporary tables are automatically filtered out. If the source database is not an OceanBase database, OMS Community Edition performs format conversion and encapsulation based on the syntax definition and standard of the type of the target tenant of OceanBase Database and then replicates the data to the target database.
Full migration	Migrates the existing data from tables in the source database to the corresponding tables in the target database. On the Full Migration page, you can view information on the Table, Table Indexes, and Migration Performance tabs. The status of a full migration task changes to Completed only after the table objects and table indexes are migrated. On the Table Indexes page, you can click View Creation Syntax next to a table to view its index creation syntax. You can combine full migration with incremental synchronization to ensure data consistency between the source and target databases. If any objects fail to be migrated during full migration, the causes of the failure are displayed.
Incremental synchronization	After incremental synchronization starts, OMS Community Edition synchronizes the data that has been changed (added, modified, or deleted) in the source database to the corresponding tables in the target database. When services continuously write data to the source database, OMS Community Edition starts the incremental data pull module to pull incremental data from the source instance, parses and encapsulates the incremental data, and then stores the data. After that, OMS Community Edition starts the full migration task. After the full migration task is completed, OMS Community Edition starts the incremental data replay module to pull incremental data from the incremental data pull module. The incremental data is synchronized to the target database after being filtered, mapped, and converted.
Full verification	After the full migration and incremental data migration are completed, OMS Community Edition automatically initiates a full verification task to verify the data tables in the source and the target. You can initiate custom data verification tasks during incremental data synchronization. If tables with inconsistent data are detected, you can choose to re-verify all data or only the inconsistent data in the tables.
Forward switchover	Forward switchover is an abstract and standard process of traditional system cutover and does not involve the switchover of application connections. This process includes a series of tasks that are performed by OMS Community Edition for application switchover in a data migration task. You must make sure that the entire forward switchover process is completed before the application connections are switched over to the target database. Forward switchover is required for data migration. OMS Community Edition can ensure the completion of forward data migration in this process. You can start the Incr-Sync component for reverse increment based on your business needs. The forward switchover process involves the following operations: You must make sure that data migration is completed and wait until forward synchronization is completed. OMS Community Edition automatically supplements CHECK constraints, FOREIGN KEY constraints, and other objects that are ignored in the schema migration phase. OMS Community Edition automatically drops the additional hidden columns and unique indexes that the migration depends on. This operation is required only when you migrate data between instances of OceanBase Database Community Edition. For more information, see Mechanisms for handling hidden columns. You must migrate triggers, functions, and stored procedures in the source database that are not supported by OMS Community Edition to the target database. You must disable triggers and drop FOREIGN KEY constraints in the source database when the data migration task involves reverse increment.
Reverse increment	In business cutover scenarios, after the migration is completed, you can start an incremental synchronization task in a reverse direction. In other words, you can synchronize data from the target database to the source database before the business database switchover. This way, data changes made in the target database after the switchover are applied to the source business database in real time.