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Terms

Updated at: 2025-02-18 03:47

This topic provides definitions for terms used in Data Transmission Service (DTS) documentation.

Term

Synonym

Description

Term

Synonym

Description

Regular instance

Single-zone instance

A DTS instance that uses a single-zone deployment solution. Its resources are deployed on machines within the same zone. When a machine in the zone fails, the DTS instance will switch to a healthy machine within the same zone to ensure the availability of the DTS instance.

Note

Currently, all DTS instances are regular instances.

Self-managed database

Self-managed database

When configuring a DTS instance, the Access Method is not a Alibaba Cloud Instance database instance. A self-managed database includes database instances from third-party clouds, databases deployed locally, and databases deployed on ECS instances.

Schema synchronization

Schema synchronization

DTS reads the structure definitions (such as tables, views, triggers, and stored procedures) of the objects to be synchronized or migrated from the source database and writes the structure definitions to the destination database. For schema synchronization or migration between heterogeneous databases, DTS converts the structure definitions to a format supported by the destination database before writing them. For example, it converts the NUMBER data type in an Oracle database to the DECIMAL data type before writing it to a MySQL database.

Schema migration

Schema migration

Full data synchronization

Full synchronization

DTS reads the historical data (data before the DTS instance starts) of the objects to be synchronized or migrated from the source database and writes all the historical data to the destination database.

Full data migration

Full migration

Incremental data synchronization

Incremental synchronization

DTS retrieves the incremental change operation statements of the objects to be synchronized or migrated from the source database (such as retrieving incremental change statements from the Binlog of a MySQL database), converts them according to the type of the destination database, and executes the statements in the destination database. This achieves real-time synchronization or migration of incremental data to the destination database. It is commonly used to achieve non-disruptive synchronization or migration, synchronizing or migrating data changes that occur during the full data synchronization or migration phase.

Important
  • When the destination database is Kafka or RocketMQ, incremental synchronization or migration will directly synchronize or migrate the data after incremental changes.

  • Incremental synchronization and incremental migration will remain in a real-time synchronization state and will not end automatically. If you need to stop incremental synchronization or incremental migration, you need to manually end or release the instance. For more information, see End DTS instance and Release DTS instance.

Incremental data migration

Incremental migration

Precheck

Precheck

To ensure the smooth operation of the DTS instance, the system performs a precheck operation before officially starting. For example, it checks whether the connectivity of the source and destination databases, database account permissions, Binlog settings, and database version numbers meet the requirements. For more information, see Introduction to precheck.

Note

If the precheck fails, you can view the details of the failure, follow the prompts to fix the issues, and then perform the precheck again.

Initial synchronization

Initial synchronization

Initial synchronization refers to the phase before starting incremental data synchronization. DTS first collects incremental data and then synchronizes the structure and historical data of the objects to be synchronized to the destination database. Initial synchronization includes incremental data collection, initial schema synchronization, and initial full data synchronization.

  • Incremental data collection: Collects data about all changes of the objects that you want to synchronize from the source database.

  • Initial schema synchronization: Synchronizes the schemas of the required objects from the source database to the destination database.

  • Initial full data synchronization: Synchronizes the historical data of objects from the source database to the destination database.

Performance

Replication performance

Refers to the number of records per second synchronized to the destination database by an incremental task. The unit is records per second (RPS). For more information, see Data synchronization link specifications, Data migration link specifications, Serverless link specifications.

Migration performance

Latency

Synchronization latency

Refers to the difference between the timestamp of the latest data synchronized or migrated to the destination database and the current timestamp of the source database. If the latency is 0, the data in the source and destination databases are fully synchronized.

Migration latency

Data update

Data update

Data update refers to operations that only modify data without changing the structure definitions. For example, INSERT, DELETE, and UPDATE operations.

Schema update

Schema update

Schema update refers to operations that modify the syntax of structure object definitions. For example, CREATE TABLE, ALTER TABLE, DROP VIEW, and other operations.

Data scope

Data scope

Data scope refers to the timestamp range of the incremental data stored in a change tracking task. By default, a change tracking task retains the data generated in the most recent 24 hours. DTS regularly deletes expired incremental data and updates the timestamp range of change tracking tasks.

Note

The timestamp of incremental data is generated when the data is updated in the source database and written to the transaction log.

Consumption checkpoint

Consumer offset

The consumption checkpoint refers to the timestamp of the latest incremental data record consumed by a client.

Each time the client consumes a data record, it returns a confirmation message to DTS. DTS updates and saves the consumption checkpoint. If the client stops responding, DTS automatically resumes data from the last consumption checkpoint and pushes the data to another consumer.

Schema task

Schema task

The task corresponding to the Schema Synchronization or Schema Migration module during runtime.

Full task

Full task

The task corresponding to the Full Data Synchronization or Full Data Migration module during runtime.

Incremental task

Incremental task

The task corresponding to the Incremental Data Synchronization or Incremental Data Migration module during runtime.

Note

A data synchronization instance by default includes an incremental task (Incremental Data Synchronization).

Data verification task

Verification task

Includes full verification tasks, incremental verification tasks, and schema verification tasks.

Task type

Task type

  • Synchronization task type: Includes schema synchronization tasks, full synchronization tasks, and incremental synchronization tasks.

  • Migration task type: Includes schema migration tasks, full migration tasks, and incremental migration tasks.

  • Verification task type: Includes full verification tasks, incremental verification tasks, and schema verification tasks.

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