Real-Time Synchronization

Real-time synchronization refers to the real-time flow of key service data from sources to destinations while consistency of data can be ensured. It is different from migration. Migration means moving your overall database from one platform to another. Synchronization refers to the continuous flow of data between different services.

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

Supported Database Types

For details about supported database types and versions and synchronization types, see Supported Databases.

Network Types

DRS supports real-time synchronization through a Virtual Private Cloud (VPC), Virtual Private Network (VPN), Direct Connect, or public network. Table 1 lists the application scenarios of each network type and required preparations, and Table 2 lists the supported network types of each synchronization scenario.

**Table 1** Network types
Network Type	Application Scenario	Preparations
VPC	Synchronization between cloud databases in the same region	The source and destination databases must be in the same region. The source and destination databases can be in either the same VPC or in different VPCs. If source and destination databases are in the same VPC, they can communicate with each other by default. Therefore, you do not need to configure a security group. If the source and destination databases are not in the same VPC, the CIDR blocks of the source and destination databases cannot be duplicated or overlapped, and the source and destination databases are connected through a VPC peering connection. DRS automatically establishes a route through a single IP address when you test the network connectivity. DRS does not support communication between the source database and destination database over a VPC across tenants. If necessary, you can create a VPC peering connection and select VPN for Network Type to enable communication between the source and destination databases. For details about how to create a VPC peering connection, see Virtual Private Cloud User Guide.
VPN	Synchronization from on-premises databases to cloud databases or between cloud databases across regions	Establish a VPN connection between your local data center and the VPC that hosts the destination database. Before synchronization, ensure that the VPN network is accessible. For more information about VPN, see Getting Started with Virtual Private Network.
Direct Connect	Synchronization from on-premises databases to cloud databases or between cloud databases across regions	Use a dedicated network connection to connect your data center to VPCs. For more information about Direct Connect, see Getting Started with Direct Connect.
Public network	Synchronization from on-premises or external cloud databases to the destination databases.	To ensure network connectivity between the source and destination databases, perform the following operations: Enable public accessibility. Enable public accessibility for the source database based on your service requirements. Configure security group rules. Add the EIPs of the synchronization instance to the whitelist of the source database for inbound traffic. If destination databases and the synchronization instance are in the same VPC, they can communicate with each other by default. Therefore, you do not need to configure a security group. NOTE: The IP address on the Configure Source and Destination Databases page is the EIP of the synchronization instance. If SSL is not enabled, synchronizing confidential data is not recommended.

**Table 2** Supported network types
Synchronization Direction	Source DB	Destination DB	VPC	Public Network	VPN or Direct Connect
To the cloud	MySQL	MySQL	Supported	Supported	Supported
		PostgreSQL	Supported	Supported	Supported
		GaussDB distributed	Supported	Supported	Supported
		GaussDB primary/standby instances NOTE: Only whitelisted users can use this function.	Supported	Supported	Supported
		GaussDB(for MySQL)	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Supported
	PostgreSQL	PostgreSQL	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Supported
		GaussDB primary/standby	Supported	Supported	Supported
		GaussDB distributed	Supported	Supported	Supported
	DDM	MySQL	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Supported
		DDM	Supported	Supported	Supported
	Oracle	MySQL	Supported	Supported	Supported
		DDM	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Supported
		PostgreSQL	Supported	Supported	Supported
		GaussDB(for MySQL)	Supported	Supported	Supported
		GaussDB primary/standby	Supported	Supported	Supported
		GaussDB distributed	Supported	Supported	Supported
	DB2 for LUW	GaussDB primary/standby instances NOTE: Only whitelisted users can use this function.	Supported	Supported	Supported
		GaussDB distributed instances NOTE: Only whitelisted users can use this function.	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Supported
	TiDB	GaussDB(for MySQL) NOTE: Only whitelisted users can use this function.	Not supported	Supported	Supported
	Microsoft SQL Server	GaussDB(DWS) NOTE: Only whitelisted users can use this function.	Supported	Supported	Supported
		GaussDB primary/standby instances NOTE: Only whitelisted users can use this function.	Supported	Supported	Supported
		GaussDB distributed instances NOTE: Only whitelisted users can use this function.	Supported	Supported	Supported
		Microsoft SQL Server NOTE: Only whitelisted users can use this function.	Supported	Supported	Supported
	MongoDB	DDS	Supported	Supported	Supported
From the cloud	MySQL	MySQL	Supported	Supported	Supported
		Kafka	Supported	Supported	Supported
		CSS/ES	Supported	Supported	Supported
		Oracle	Supported	Supported	Supported
	DDM	MySQL	Supported	Supported	Supported
		Oracle	Supported	Supported	Supported
		Kafka	Supported	Supported	Supported
	DDS	MongoDB	Supported	Supported	Supported
	PostgreSQL	Kafka	Not supported	Supported	Supported
	GaussDB primary/standby	MySQL NOTE: Only whitelisted users can use this function.	Not supported	Supported	Supported
		Oracle	Not supported	Supported	Supported
		Kafka	Supported	Supported	Supported
		GaussDB(DWS)	Not supported	Supported	Supported
		GaussDB distributed	Supported	Supported	Supported
		GaussDB primary/standby	Supported	Supported	Supported
	GaussDB distributed	MySQL	Not supported	Supported	Supported
		Oracle	Not supported	Supported	Supported
		GaussDB(DWS)	Not supported	Supported	Supported
		Kafka	Supported	Supported	Supported
		GaussDB distributed	Supported	Supported	Supported
		GaussDB primary/standby	Supported	Supported	Supported
	GaussDB(for MySQL)	MySQL	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Supported
		Kafka	Supported	Supported	Supported
		CSS/ES	Supported	Supported	Supported
		Oracle	Supported	Supported	Supported
Self-built -> Self-built	MySQL	Kafka	Supported	Supported	Supported
	MySQL	CSS/ES	Supported	Supported	Supported
	Oracle	Kafka	Supported	Supported	Supported
		GaussDB primary/standby instances	Not supported	Supported	Supported
		GaussDB distributed instances	Not supported	Supported	Supported
	PostgreSQL	Kafka	Not supported	Supported	Supported
	GaussDB primary/standby instances	Oracle	Not supported	Supported	Supported
	GaussDB primary/standby instances	Kafka	Supported	Supported	Supported
	GaussDB distributed instances	Oracle	Not supported	Supported	Supported
	GaussDB distributed instances	Kafka	Supported	Supported	Supported

Supported Synchronization Objects

DRS allows you to synchronize different objects. The following table lists the supported objects.

**Table 3** Supported synchronization objects
Synchronization Direction	Source DB	Destination DB	Table-level	Database-level	Importing an Object File
To the cloud	MySQL	MySQL	Supported	Supported	Supported
		PostgreSQL	Supported	Supported	Supported
		GaussDB distributed	Supported	Not supported	Not supported
		GaussDB primary/standby instances NOTE: Only whitelisted users can use this function.	Supported	Not supported	Supported
		GaussDB(for MySQL)	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Supported
	PostgreSQL	PostgreSQL	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Not supported
		GaussDB primary/standby instances	Supported	Not supported	Not supported
		GaussDB distributed	Supported	Not supported	Not supported
	DDM	MySQL	Supported	Not supported	Not supported
		GaussDB(DWS)	Supported	Supported	Not supported
		DDM	Supported	Supported	Not supported
	Oracle	MySQL	Supported	Supported	Supported
		DDM	Supported	Not supported	Not supported
		GaussDB(DWS)	Supported	Not supported	Supported
		PostgreSQL	Supported	Not supported	Supported
		GaussDB(for MySQL)	Supported	Supported	Supported
		GaussDB primary/standby	Supported	Supported	Supported
		GaussDB distributed	Supported	Supported	Supported
	DB2 for LUW	GaussDB primary/standby instances NOTE: Only whitelisted users can use this function.	Supported	Not supported	Supported
		GaussDB distributed instances NOTE: Only whitelisted users can use this function.	Supported	Not supported	Supported
		GaussDB(DWS)	Supported	Not supported	Supported
	TiDB	GaussDB(for MySQL) NOTE: Only whitelisted users can use this function.	Supported	Supported	Not supported
	Microsoft SQL Server	GaussDB(DWS) NOTE: Only whitelisted users can use this function.	Supported	Not supported	Not supported
		GaussDB primary/standby instances NOTE: Only whitelisted users can use this function.	Supported	Not supported	Not supported
		GaussDB distributed instances NOTE: Only whitelisted users can use this function.	Supported	Not supported	Not supported
		Microsoft SQL Server NOTE: Only whitelisted users can use this function.	Supported	Not supported	Not supported
	MongoDB	DDS	Supported	Supported	Not supported
From the cloud	MySQL	MySQL	Supported	Supported	Not supported
		Kafka	Supported	Supported	Supported
		CSS/ES	Supported	Not supported	Supported
		Oracle	Supported	Not supported	Supported
	DDM	MySQL	Supported	Not supported	Not supported
		Oracle	Supported	Supported	Not supported
		Kafka	Supported	Supported	Not supported
	DDS	MongoDB	Supported	Supported	Not supported
	PostgreSQL	Kafka	Supported	Supported	Not supported
	GaussDB primary/standby	MySQL NOTE: Only whitelisted users can use this function.	Supported	Not supported	Not supported
		Oracle	Supported	Not supported	Supported
		Kafka	Supported	Not supported	Not supported
		GaussDB(DWS)	Supported	Not supported	Not supported
		GaussDB distributed	Supported	Not supported	Supported
		GaussDB primary/standby	Supported	Not supported	Supported
	GaussDB distributed	MySQL	Supported	Not supported	Not supported
		Oracle	Supported	Not supported	Supported
		GaussDB(DWS)	Supported	Not supported	Not supported
		Kafka	Supported	Not supported	Not supported
		GaussDB distributed	Supported	Not supported	Supported
		GaussDB primary/standby	Supported	Not supported	Supported
	GaussDB(for MySQL)	MySQL	Supported	Supported	Supported
		GaussDB(DWS)	Supported	Supported	Supported
		Kafka	Supported	Supported	Supported
		CSS/ES	Supported	Supported	Not supported
		Oracle	Supported	Not supported	Supported
Self-built -> Self-built	MySQL	Kafka	Supported	Supported	Supported
	MySQL	CSS/ES	Supported	Not supported	Supported
	Oracle	Kafka	Supported	Not supported	Supported
		GaussDB primary/standby	Supported	Supported	Supported
		GaussDB distributed	Supported	Supported	Supported
	GaussDB primary/standby instances	Oracle	Supported	Not supported	Supported
	GaussDB primary/standby instances	Kafka	Supported	Not supported	Not supported
	GaussDB distributed instances	Oracle	Supported	Not supported	Supported
	GaussDB distributed instances	Kafka	Supported	Not supported	Not supported
	PostgreSQL	Kafka	Supported	Supported	Not supported

Advanced Features

DRS supports multiple features to ensure successful data synchronization.

**Table 4** Advanced features
Feature	Description
Synchronization level	DRS supports database- and table-level synchronization. Database-level synchronization refers to a type of synchronization method using database as a unit. You do not need to select tables to be synchronized. New tables in the database are automatically added to the synchronization task. Table-level synchronization uses table as a unit, indicating that you need to add new tables to the synchronization task manually.
Mapping object names	Allows the names of synchronization objects (including databases, schemas, tables, and columns) in the source database to be different from those in the destination database. If the synchronization objects in source and destination databases have different names, you can map the source object name to the destination one. The following objects can be mapped: databases, schemas and tables.
Dynamically adding or deleting synchronization objects	During data synchronization, you can add or delete synchronization objects as required.
Conflict policy	DRS uses primary key or unique key conflict policies to ensure that tables with primary key or unique constraints in the source database can be synchronized to the destination database as expected. The following conflict policies are supported: Ignore The system will skip the conflicting data and continue the subsequent synchronization process. Overwrite Conflicting data will be overwritten. Report error The synchronization task will be stopped and fail. Ignore and overwrite: Synchronization stability is prioritized, so tasks will not be interrupted as data conflicts occur. Report error: Data quality is prioritized. Any data conflicts are not allowed, so once a conflict occurs, the synchronization task fails and an error is reported. You need to manually find the cause of the fault. If the task is in the failed state for a long time, the storage space may be used up and the task cannot be restored.
Structure synchronization	DRS does not provide data structure synchronization as an independent function during real-time synchronization. Instead, it directly synchronizes data and structures to the destination database.