Migrate MongoDB (standalone instance) to MongoDB (all architectures) - Data Transmission Service

This topic explains how to use Data Transmission Service (DTS) for a full migration from a MongoDB database (standalone instance) to a MongoDB database (all architectures).

Supported source and destination databases

Source database (standalone instance)	Destination database (all architectures)
Cloud Database MongoDB Edition	Cloud Database MongoDB Edition
Self-managed database on ECS	Self-managed database on ECS
Self-managed database accessed through leased line, VPN Gateway, or Smart Gateway	Self-managed database accessed through leased line, VPN Gateway, or Smart Gateway
Self-managed database with a public IP address	Self-managed database with a public IP address

This topic illustrates the configuration process using Cloud Database MongoDB Edition (standalone instance) and Cloud Database MongoDB Edition (all architectures) as examples. The process for configuring other data sources follows a similar pattern.

Prerequisites

The source Cloud Database MongoDB Edition (standalone instance) and the target Cloud Database MongoDB Edition (all architectures) are already set up. For details on how to create these, see Create a standalone instance, Create a replica set instance, and Create a sharded cluster instance.
Note
For a list of supported versions, refer to the migration solution overview.
It is advisable to ensure that the destination Cloud Database MongoDB Edition has a storage capacity at least 10% greater than that of the source Cloud Database MongoDB Edition.
If the destination Cloud Database MongoDB Edition utilizes a sharded cluster architecture, you must create the necessary databases and collections for sharding in the destination Cloud Database MongoDB Edition based on your business requirements. This process involves configuring data sharding, activating the Balancer, and executing pre-sharding operations. For more information, see how to optimize shard performance through data sharding and how to manage uneven data distribution in MongoDB's sharded cluster architecture.
Note
Configuring data sharding helps avoid data migration to the same shard, which could degrade cluster performance. Enabling the Balancer and pre-sharding can prevent data skew.

Notes

Category	Description
Limits on the source database	Bandwidth requirements: The server on which the source database is deployed must have sufficient outbound bandwidth. Otherwise, the data migration speed decreases. The collections to be migrated must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records. If you select collections as the objects to be migrated and you need to edit collections in the destination database, such as renaming collections, up to 1,000 collections can be migrated in a single data migration task. If you run a task to migrate more than 1,000 collections, a request error occurs. In this case, we recommend that you configure multiple tasks to migrate the collections in batches or configure a task to migrate the entire database. The size of a single data entry in the source database cannot exceed 16 MB. Otherwise, the data migration task fails. Limits on operations to be performed on the source database: During schema migration and full data migration, do not perform schema change on databases or collections, including the update of the array type. Otherwise, the data migration task fails, or data inconsistency between the source and destination databases may occur. Incremental data migration is not supported in this scenario. To ensure data consistency, we recommend that you do not write data to the source MongoDB database during full data migration. You cannot migrate collections that contain time to live (TTL) indexes. If the source database contains TTL indexes, data inconsistency may occur between the source and destination databases after the migration.
Other limits	If the destination database is a sharded cluster database, take note of the following limits: Orphaned documents must be deleted. Otherwise, the migration performance is compromised. During data migration, if a `_id` conflict exists in the documents of the source and destination databases, data inconsistency may occur, or the data migration task may fail. Before you start the data migration task, you must add shard keys to the data to be migrated in the source database. If you cannot add shard keys to the data in the source database, you can migrate data from a MongoDB database without shard keys. For more information, see Migrate data from a MongoDB instance without a sharding key to a MongoDB sharded cluster instance. During the data migration, if you execute the INSERT statement to insert data into the data to be migrated, the data to be migrated must contain shard keys. If you execute the UPDATE statement to modify the data to be migrated, you cannot modify shard keys. If the destination database is a replica set instance, take note of the following limits: If the destination database is connected over Express Connect, VPN Gateway, or Smart Access Gateway, Public IP Address, or Cloud Enterprise NetworkCEN, set the Domain Name or IP and Port Number to the IP address and the port number of primary node, or configure a high-availability endpoint. For more information about high-availability endpoints, see Create a DTS task in which the source or destination database is a high-availability MongoDB database. If the destination database is connected over Self-managed Database on ECS, set the Port Number to the port number of primary node. Incremental data migration is not supported. DTS cannot connect MongoDB database over a SRV endpoint. If a collection of the destination database has a unique index or the `capped` attribute of a collection of the destination database is `true`, the collection supports only single-thread data writing and does not support concurrent replay during incremental data migration. This may increase migration latency. DTS cannot migrate data from the admin or local database. Transaction information is not retained. When transactions are migrated to the destination database, the transactions are converted into a single record. If a primary key or a unique key conflict occurs during which DTS writes data to the destination collection, DTS skips the statements used to write data and retain the existing data in the destination collection. To ensure compatibility, the version of the destination MongoDB database must be the same as or later than the version of the source MongoDB database. If the version of the destination database is earlier than the version of the source database, database compatibility issues may occur. Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads on the database servers. During full data migration, concurrent INSERT operations cause fragmentation in the collections of the destination database. After full data migration is complete, the storage space for collections of the destination database is larger than that of the source database. You must make sure that the precision settings for columns of the FLOAT or DOUBLE data type meet your business requirements. DTS uses the `ROUND(COLUMN,PRECISION)` function to retrieve values from columns of the FLOAT or DOUBLE data type. If you do not specify a precision, DTS sets the precision for the FLOAT data type to 38 digits and the precision for the DOUBLE data type to 308 digits. DTS attempts to resume a data migration task that failed within the last seven days. Before you switch workloads to the destination cluster, you must stop or release the failed tasks. You can also execute the `REVOKE` statement to revoke the write permissions from the accounts that are used by DTS to access the destination database. Otherwise, the data in the source database overwrites the data in the destination database after the data migration task is resumed. The data is concurrently written to the destination database. Therefore, the storage space occupied in the destination database is 5% to 10% larger than the size of the data in the source database. You must use the `db.$table_name.aggregate([{ $count:"myCount"}])` syntax to query the return value of a count operation on the destination MongoDB database. Make sure that the destination MongoDB database does not have the same primary key as the source database. The default primary key is _id. Otherwise, data may be lost. If the data in the destination database has the same primary key as that in the source database, clear the related data in the destination database without interrupting the services of DTS. For example, if the same primary key is _id, you can delete the data in the destination database that has the same _id as the source database. If a DTS task fails to run, DTS technical support will try to restore the task within 8 hours. During the restoration, the task may be restarted, and the parameters of the task may be modified. Note Only the parameters of the task may be modified. The parameters of databases are not modified. The parameters that may be modified include but are not limited to the parameters in the "Modify instance parameters" section of the Modify the parameters of a DTS instance topic. If you migrate data to another MongoDB database (sharded cluster architecture), make sure that your business behavior meets the requirements of the ApsaraDB for MongoDB sharded cluster.
Special cases	If the source database is a self-managed MongoDB database, we recommend that you do not perform a primary/secondary switchover on the source database when the data migration task is running. Otherwise, the task fails.

Billing

Migration type	Instance configuration fee	Internet traffic fee
Schema migration and full data migration	Free of charge.	When the Access Method parameter of the destination database is set to Public IP Address, you are charged for Internet traffic. For more information, see Billing overview.

Migration types

Migration type	Description
Schema migration	Migrate the structure of the migration objects in the source Cloud Database MongoDB Edition to the destination Cloud Database MongoDB Edition. Note The objects that support schema migration are DATABASE, COLLECTION, and INDEX.
Full migration	Migrate all historical data of the migration objects in the source Cloud Database MongoDB Edition to the destination Cloud Database MongoDB Edition. Note Full migration supports data in DATABASE and COLLECTION.

Permissions required for database accounts

Database	Schema migration	Full migration
Source Cloud Database MongoDB Edition	Read permissions on the database to be migrated and the config database.
Destination Cloud Database MongoDB Edition	dbAdminAnyDatabase permission, read and write permissions on the destination database, and read permissions on the local database.

For details on creating and granting permissions to database accounts for both source and destination Cloud Database MongoDB Edition, refer to Managing MongoDB Database Users with DMS.

Procedure

Use one of the following methods to go to the Data Migration page and select the region in which the data migration instance resides.
DTS console
1. Log on to the DTS console.
2. In the left-side navigation pane, click Data Migration.
3. In the upper-left corner of the page, select the region in which the data migration instance resides.
DMS console
Note
The actual operation may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.
1. Log on to the DMS console.
2. In the top navigation bar, move the pointer over Data + AI > DTS (DTS) > Data Migration.
3. From the drop-down list to the right of Data Migration Tasks, select the region in which the data synchronization instance resides.
Click Create Task to go to the task configuration page.
Optional. Click New Configuration Page in the upper-right corner of the page.
Note
- Skip this step if the Back to Previous Version button is displayed in the upper-right corner of the page.
- Specific parameters in the new and previous versions of the configuration page may be different. We recommend that you use the new version of the configuration page.

Configure the source and destination databases. The following table describes the parameters.

Warning

After you configure the source and destination databases, we recommend that you read the Limits that are displayed in the upper part of the page. Otherwise, the task may fail or data inconsistency may occur.

Category	Configuration	Description
None	Task Name	The name of the DTS task. DTS automatically generates a task name. We recommend that you specify an informative name that makes it easy to identify the task. You do not need to specify a unique task name.
Source Database Information	Select Existing Connection	If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections. Note In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list. If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.
	Database Type	Select MongoDB.
	Access Method	Select Cloud Instance.
	Instance Region	Select the region where the source Cloud Database MongoDB Edition resides.
	Replicate Data Across Alibaba Cloud Accounts	In this example, a database instance of the current Alibaba Cloud account is used. Select No.
	Architecture Type	For MongoDB with standalone instance architecture, select Replica Set Architecture. Replica Set Architecture: Achieves high availability and read/write splitting by deploying multiple nodes. For more information, see Replica set architecture. Sharded Cluster Architecture: Provides three components: Mongos, Shard, and ConfigServer. You can freely choose the number and configuration of Mongos and Shard. For more information, see Sharded cluster architecture.
	Migration Method	When the source database is a standalone instance architecture of MongoDB, incremental migration is not supported. Keep the default Oplog.
	Instance ID	Select the instance ID of the source Cloud Database MongoDB Edition.
	Authentication Database Name	Enter the name of the database to which the database account of the source Cloud Database MongoDB Edition instance belongs. If it has not been modified, the default is admin.
	Database Account	Enter the database account of the source Cloud Database MongoDB Edition. For permission requirements, see Permissions required for database accounts.
	Database Password	The password that is used to access the database instance.
	Encryption	Specifies whether to encrypt the connection to the source database. You can select Non-encrypted, SSL-encrypted, or Mongo Atlas SSL based on your business requirements. The options available for the Encryption parameter are determined by the values selected for the Access Method and Architecture parameters. The options displayed in the DTS console prevail. Note If the Architecture parameter is set to Sharded Cluster, and the Migration Method parameter is set to Oplog for the ApsaraDB for MongoDB database, the Encryption parameter SSL-encrypted is unavailable. If the source database is a self-managed MongoDB database that uses the Replica Set architecture, the Access Method parameter is not set to Alibaba Cloud Instance, and the Encryption parameter is set to SSL-encrypted, you can upload a certification authority (CA) certificate to verify the connection to the source database.
Destination Database	Select Existing Connection	If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections. Note In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list. If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.
	Database Type	Select MongoDB.
	Access Method	Select Cloud Instance.
	Instance Region	Select the region where the destination Cloud Database MongoDB Edition resides.
	Replicate Data Across Alibaba Cloud Accounts	In this example, a database instance of the current Alibaba Cloud account is used. Select No.
	Architecture Type	Select the architecture based on your business needs. Valid values: Replica Set Architecture: Achieves high availability and read/write splitting by deploying multiple nodes. For more information, see Replica set architecture. Sharded Cluster Architecture: Provides three components: Mongos, Shard, and ConfigServer. You can freely choose the number and configuration of Mongos and Shard. For more information, see Sharded cluster architecture.
	Instance ID	Select the instance ID of the destination Cloud Database MongoDB Edition.
	Authentication Database Name	Enter the name of the database to which the database account of the destination Cloud Database MongoDB Edition belongs. If it has not been modified, the default is admin.
	Database Account	Enter the database account of the destination Cloud Database MongoDB Edition. For permission requirements, see Permissions required for database accounts.
	Database Password	The password that is used to access the database instance.
	Encryption	Specifies whether to encrypt the connection to the destination database. You can select Non-encrypted, SSL-encrypted, or Mongo Atlas SSL based on your business requirements. The options available for the Encryption parameter are determined by the values selected for the Access Method and Architecture parameters. The options displayed in the DTS console prevail. Note If the destination database is an ApsaraDB for MongoDB instance and the Architecture parameter is set to Sharded Cluster, the Encryption parameter SSL-encrypted is unavailable. If the destination database is a self-managed MongoDB database that uses the Replica Set architecture, the Access Method parameter is not set to Alibaba Cloud Instance, and the Encryption parameter is set to SSL-encrypted, you can upload a CA certificate to verify the connection to the destination database.

In the lower part of the page, click Test Connectivity and Proceed.
Note
- Make sure that the CIDR blocks of DTS servers can be automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add the CIDR blocks of DTS servers.
- If the source or destination database is a self-managed database and its Access Method is not set to Alibaba Cloud Instance, click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

Configure the objects to be migrated.

On the Configure Objects page, configure the objects that you want to migrate.

Configuration	Description
Migration Types	Select Schema Migration and Full Data Migration. Note In this scenario, DTS does not support incremental data migration. To ensure data consistency, we recommend that you do not write data to the source database during data migration. For more information, see Migration 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 the precheck, and the data migration task cannot be started. Note You can use the object name mapping feature to rename the collections that are migrated to the destination database. You can use this feature if the source and destination databases contain identical collection names and the collections in the destination database cannot be deleted or renamed. For more information, see Map object names. 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 migrate data records that have the same primary keys as data records in the destination database. Data may fail to be initialized, only some columns are migrated, or the data migration task fails.
Capitalization of Object Names in Destination Instance	You can set the case policy for database and collection names of the objects being migrated to the destination instance. By default, the DTS Default Policy is applied. Alternatively, you may opt to align the default policy with that of the source and destination databases. For more information, see Case policy for object names in the destination database.
Source Objects	In the Source Database Objects box, select the object you want to migrate, and then click to transfer it to the Selected Objects box. Note Migration object selection granularity is at the DATABASE and COLLECTION level.
Selected Objects	To specify the name of an object to be migrated in the destination instance or specify the object to receive data in the destination instance, right-click the object in the Selected Objects section. For more information, see Map object names. To remove one or more objects that are selected for migration, click the objects in the Selected Objects section and then click the icon to move the objects to the Source Objects section. Note To select the incremental migration mode for databases and collections, right-click objects to be migrated in the Selected Objects section and then select the mode in the dialog box that appears. To specify WHERE conditions to filter data, right-click a table in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Specify filter conditions. You can specify WHERE conditions during full migration but not incremental migration. If you use the object name mapping feature to specify databases or collections for receiving data, other objects depending on the specified objects may fail to be migrated.

Click Next: Advanced Settings to configure advanced settings.

Configuration	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules the data migration task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data migration tasks, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.
Retry Time for Failed Connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1,440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later 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 requirements. You can also release the DTS instance at the earliest opportunity after the source database and destination instance are released.
Retry Time for Other Issues	The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Important The value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
Enable Throttling for Full Data Migration	Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters. This reduces the loads of the destination database server. Note You can configure this parameter only if you select Full Data Migration for the Migration Types parameter.
Only one data type for primary key _id in a table of the data to be synchronized	Specifies whether the data type of the primary key `_id` is unique in a collection to be migrated. Important Enable this parameter based on your business requirements. Otherwise, data loss may occur. This parameter is required only if you select Full Data Migration for the Migration Types parameter. Valid values: Yes: The data type is unique. During full migration, DTS does not scan the data type of the primary key in source database. DTS only migrates a data type of the primary key in a collection to be migrated. No: The data type is not unique. During full migration, DTS scans the data types of the primary key in source database and migrates the data of all data types.
Enable Throttling for Incremental Data Migration	Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server. Note You can configure this parameter only if you select Incremental Data Migration for the Migration Types parameter.
Environment Tag	Select an environment tag to identify the instance as needed. In this case, no tag is selected.
Configure ETL	Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: configures the ETL feature. You can enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: does not configure the ETL feature.
Monitoring and Alerting	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values: No: does not configure alerting. Yes: configures alerting. In this case, you must also configure the alert threshold and alert notification settings. For more information, see the Configure monitoring and alerting when you create a DTS task section of the Configure monitoring and alerting topic.

Click Next Step: Data Verification to configure the data verification task.
For more information about how to use the data verification feature, see Configure a data verification task.

Save the task settings and run a precheck.
- To view the parameters to be specified when you call the relevant API operation to configure the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.
- If you do not need to view or have viewed the parameters, click Next: Save Task Settings and Precheck in the lower part of the page.
Note
- Before you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.
- If the task fails to pass the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.
- If an alert is triggered for an item during the precheck:
  If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.
  If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.

Purchase an instance.

Wait until Success Rate becomes 100%. Then, click Next: Purchase Instance.

On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

Section	Parameter	Description
New Instance Class	Resource Group	The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Instance classes of data migration instances.

Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.
Click Buy and Start. In the message that appears, click OK.
You can view the progress of the task on the Data Migration page.
Note
- If a data migration task cannot be used to migrate incremental data, the task automatically stops. The Completed is displayed in the Status section.
- If a data migration task can be used to migrate incremental data, the task does not automatically stop. The incremental data migration task never stops or completes. The Running is displayed in the Status section.