From DDM to DDM¶
Supported Source and Destination Databases¶
Source DB | Destination DB |
---|---|
|
|
Prerequisites¶
You have logged in to the DRS console.
For details about the DB types and versions supported by real-time synchronization, see Real-Time Synchronization.
Suggestions¶
Caution
When a 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.
To keep data consistency before and after the synchronization, ensure that no data is written to the destination database during the synchronization.
The success of database synchronization depends on environment and manual operations. To ensure a smooth synchronization, perform a synchronization trial before you start the synchronization to help you detect and resolve problems in advance.
Start your synchronization task during off-peak hours. A less active database is easier to synchronize successfully. If the data is fairly static, there is less likely to be any severe performance impacts during the synchronization.
If network bandwidth is not limited, the query rate of the source database increases by about 50 MB/s during full synchronization, and two to four CPUs are occupied.
The data being synchronized may be locked by other transactions for a long period of time, resulting in read timeout.
When DRS concurrently reads data from a database, it will use about 6 to 10 sessions. The impact of the connections on services must be considered.
If you read a table, especially a large table, during the full migration, the exclusive lock on that table may be blocked.
Data-Level Comparison
To obtain accurate comparison results, start data comparison at a specified time point during off-peak hours. If it is needed, select Start at a specified time for Comparison Time. Due to slight time difference and continuous operations on data, data inconsistency may occur, reducing the reliability and validity of the comparison results.
Precautions¶
Before creating a synchronization task, read the following notes:
Note
You are advised to create an independent database account for DRS task connection to prevent task failures caused by account modification.
After changing the account passwords for the source or destination databases, modify the connection information in the DRS task as soon as possible to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.
Type | Restrictions |
---|---|
Database permissions |
|
Synchronization object |
|
Source database |
|
Destination database |
|
Precautions |
|
Procedure¶
On the Data Synchronization Management page, click Create Synchronization Task.
On the Create Synchronization Instance page, specify the task name, description, and the synchronization instance details, and click Next.
Task information description
¶ Parameter
Description
Region
The region where the synchronization instance is deployed. You can change the region.
Project
The project corresponds to the current region and can be changed.
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
¶ Parameter
Description
Data Flow
Select To the cloud.
Source DB Engine
Select DDM.
Destination DB Engine
Select DDM.
Network Type
The public network is used as an example. Available options: Public network, VPC, VPN or Direct Connect
Destination DB Instance
The DDM instance you created.
Synchronization Instance Subnet
Select the subnet where the synchronization instance is located. You can also click View Subnet 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 ensure that there are available IP addresses. To ensure that the synchronization instance is successfully created, only subnets with DHCP enabled are displayed.
Synchronization Mode
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.
Source DB Instance Quantity
Specifies the number of DB instances bound to the source DDM database. The default value is 2. The value ranges from 1 to 64. Set this parameter based on the site requirements.
Note
After a task is created, DRS creates subtasks, whose quantity is the same as the number of source DB instances. Each subtask migrates data from its source database to the destination database.
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.
After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.
Note
If a task fails to be created, DRS retains the task for three days by default. After three days, the task automatically ends.
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.
¶ Parameter
Description
Middleware IP Address or Domain Name
The IP address or domain name of the source DDM middleware.
Port
The port of the source DDM middleware. Value range: 1 to 65535
Middleware Username
The username of the source DDM instance.
Middleware Password
The password for the source DDM instance username.
SSL Connection
SSL encrypts the connections between the source and destination databases. If SSL is enabled, upload the SSL CA root certificate.
Note
The maximum size of a single certificate file that can be uploaded is 500 KB.
If the SSL certificate is not used, your data may be at risk.
DB Instance
The sharded database details.
Note
The IP address, domain name, username, and password of the source database are encrypted and stored in DRS, and will be cleared after the task is deleted.
¶ Parameter
Description
DB Instance Name
The DDM instance you selected when you create a synchronization task. The instance name 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.
On the Set Synchronization Task page, select the objects to be synchronized, and then click Next.
¶ Parameter
Description
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.
Synchronization Object
Select Tables, Databases, or Import object file 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. For details, see Mapping Object Names.
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.
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.
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.
Note
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.
On the Confirm Task page, specify Start Time, confirm that the configured information is correct, and click Submit to submit the task.
¶ Parameter
Description
Started 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.
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.