Data Transmission Service:Synchronize data from an ApsaraDB for MongoDB instance (replica set architecture) to another ApsaraDB for MongoDB instance (replica set architecture or sharded cluster architecture)

Supported source and destination databases

Prerequisites

• The source ApsaraDB for MongoDB instance (replica set architecture) and the destination ApsaraDB for MongoDB instance (replica set architecture or sharded cluster architecture) are created. For more information, see Create a replica set instance and Create a sharded cluster instance.
  Note For more information about supported MongoDB versions, see Overview of data synchronization scenarios.
• The available storage space of the destination ApsaraDB for MongoDB instance is larger than the total size of the data in the source ApsaraDB for MongoDB instance.
• If the destination ApsaraDB for MongoDB instance is deployed in a sharded cluster architecture, you must create databases and collections to be sharded in the destination ApsaraDB for MongoDB instance and configure sharding based on your business needs. For more information, see Configure sharding to maximize the performance of shards.
  Note

  • After you configure sharding for a cluster, the synchronized data will be distributed among different shards. This maximizes the performance of the sharded cluster.
  • The shard nodes in a sharded cluster instance must share the same account password and endpoint. For more information, see Apply for an endpoint for a shard or Configserver node.

Limits

Billing

Supported synchronization topologies

• One-way one-to-one synchronization
• One-way one-to-many synchronization
• One-way many-to-one synchronization
• One-way cascade synchronization

Synchronization types

Procedure

1. Go to the Data Synchronization page of the new DTS console.
   Note You can also log on to the Data Management console. In the top navigation bar, click DTS. Then, in the left-side navigation pane, choose DTS (DTS) > Data Synchronization.
2. In the upper-left corner of the page, select the region where the data synchronization instance resides.
   
3. Click Create Task. On the page that appears, configure the source and destination databases.
   Warning After you select the source and destination instances, we recommend that you read the Limits displayed in the upper part of the page. This ensures that you create and run the data synchronization task.

   Section	Parameter	Description
   N/A	Task Name	The task name that DTS automatically generates. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to use a unique task name.
   Source Database
   	Database Type	Select MongoDB.
   	Access Method	Select Cloud Instance.
   	Instance Region	Select the region where the source ApsaraDB for MongoDB instance resides.
   	Instance ID	Select the ID of the source ApsaraDB for MongoDB instance.
   	Database Name	Enter admin. Note Enter the name of the authentication database. The database account is created in this database.
   	Database Account	Enter the database account of the source ApsaraDB for MongoDB instance. The account must have the read permissions on the source database, admin database, and local database.
   	Database Password	The password of the database account.
   Destination Database
   	Database Type	Select MongoDB.
   	Access Method	Select Alibaba Cloud Instance.
   	Instance Region	Select the region where the destination ApsaraDB for MongoDB instance resides.
   	Instance ID	Select the ID of the destination ApsaraDB for MongoDB instance.
   	Database Name	Enter admin. Note Enter the name of the authentication database. The database account is created in this database.
   	Database Account	Enter the database account of the destination ApsaraDB for MongoDB instance. The account must have the dbAdminAnyDatabase permission, the read and write permissions on the destination database, and the read permissions on the local database.
   	Database Password	The password of the database account.

4. In the lower part of the page, click Test Connectivity and Proceed.
   Note

   • You do not need to modify the security settings for ApsaraDB instances (such as ApsaraDB RDS for MySQL and ApsaraDB for MongoDB) and ECS-hosted databases. DTS automatically adds the CIDR blocks of DTS servers to the whitelists of ApsaraDB instances or the security group rules of ECS instances. For more information, see Add the CIDR blocks of DTS servers to the security settings of on-premises databases.
   • After data synchronization is complete, we recommend that you remove the CIDR blocks of DTS servers from the whitelists or security groups.
5. Select the objects to migrate.
   • Basic Settings

     Parameter	Description
     Task Stages	Incremental Data Synchronization is selected by default. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of selected objects from the source instance to the destination cluster. The historical data is the basis for subsequent incremental synchronization. Note For more information, see Synchronization types.
     Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains collections that have the same names as collections in the source database. If the source and destination databases do not contain identical collection names, the precheck is passed. Otherwise, an error is returned during precheck and the data synchronization task cannot be started. Note If the source and destination databases contain identical collection names and the collections in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the collections that are synchronized to the destination database. For more information, see Rename an object to be synchronized. Ignore Errors and Proceed: skips the precheck for identical collection names in the source and destination databases. Warning If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to potential risks. DTS does not synchronize data records that have the same primary keys as data records in the destination database. Data may fail to be initialized, only part of columns are synchronized, or the data synchronization task fails.
     Select Objects	Select one or more objects from the Source Objects section and click the icon to add the objects to the Selected Objects section. Note You can select databases or collections as the objects to be synchronized.
     Rename Databases and Tables	To rename an object in the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object. To rename multiple objects at a time in the destination instance, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
     Filter data	You can specify WHERE conditions to filter data. For more information, see Use SQL conditions to filter data.
     Select the SQL operations to be synchronized	In the Selected Objects section, right-click an object. In the dialog box that appears, select the SQL operations that you want to synchronize. For more information, see

   • Advanced Settings

     Parameter	Description
     Set Alerts	Specifies whether to set alerts for the data synchronization task. If you select yes, DTS sends notifications to contacts if the task fails or the synchronization latency exceeds the upper limit. No: does not set alerts. Yes: sets alerts. In this case, you must also set the alert threshold and alert contacts.
     Capitalization of Object Names in Destination Instance	Specifies the capitalization of database names and collection names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of the source or destination database. For more information,see Specify the capitalization of object names in the destination instance.
     Retry Time for Failed Connection	Specifies the retry time range for failed connections. Valid values: 10 to 1440. Unit: minutes. Default value: 120. We recommend that you set the retry time range to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails. Note If an instance serves as the source or destination database of multiple data synchronization tasks, the less value that is specified for the instance takes precedence. When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business needs. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.

6. Click Next: Save Task Settings and Precheck in the lower part of the page.
   Note

   • Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.
   • If the task fails to pass the precheck, you can click the icon next to each failed item to view details.
     • After you troubleshoot the issues based on the causes, you can run a precheck again.
     • If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
7. Wait until the Success Rate becomes 100%. Then, click Next: Purchase Instance.
8. On the Purchase Instance page, specify the billing method and specifications for the data synchronization instance. The following table describes related parameters.

   Section	Parameter	Description
   Parameters	Billing method	Subscription: You pay for your subscription when you create an instance. The subscription billing method is more cost-effective than the pay-as-you-go billing method for long-term use. Pay-as-you-go: A pay-as-you-go instance is billed on an hourly basis. For short-term use, we recommend that you select the pay-as-you-go billing method. If you no longer need a pay-as-you-go instance, you can release the instance to reduce costs.
   	Instance Class	DTS provides several instance classes that have different performance in synchronization speed. You can select an instance class based on your business scenario. For more information, see Specifications of data synchronization instances.
   	Subscription Duration	If you select the subscription billing method, set the subscription duration and the number of instances that you want to create. The subscription duration can be one to nine months or one to three years. Note This parameter is available only if you select the subscription billing method.

9. Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
10. Click Buy and Start to start the data synchronization task. You can view the progress of the task in the task list.