Synchronize data from a self-managed SQL Server database to an RDS PostgreSQL instance - Data Transmission Service

You can use Data Transmission Service (DTS) to synchronize data from a SQL Server database to an RDS PostgreSQL instance. This topic describes how to synchronize data from a SQL Server database on an Elastic Compute Service (ECS) instance .

Important

This feature is available only in the China (Qingdao), China (Beijing), and China (Hong Kong) regions.

Prerequisites

A destination RDS PostgreSQL instance is created. The available storage space of this instance must be larger than the storage space occupied by the source SQL Server database. For more information, see Quickly create an ApsaraDB RDS for PostgreSQL instance.
Note
For information about the supported versions of the source and destination databases, see Overview of data synchronization scenarios.
A database is created in the destination RDS PostgreSQL instance to store the synchronized data. For more information, see Create a database.
If the source instance meets any of the following conditions, we recommend that you split the synchronization task into multiple, smaller tasks.
- The data to be synchronized involves multiple schemas.
- A single database of the source instance backs up its logs more than once per hour.
- A single database of the source instance executes more than 100 DDL statements per hour.
- Logs are written at a rate of more than 20 MB/s for a single database of the source instance.
- The change data capture (CDC) feature needs to be enabled for more than 1,000 tables.

Usage notes

Note

During schema synchronization, DTS synchronizes foreign keys from the source database to the destination database.
During full data synchronization and incremental data synchronization, DTS temporarily disables the constraint check and cascade operations on foreign keys at the session level. If you perform the cascade update and delete operations on the source database during data synchronization, data inconsistency may occur.

Type	Description
Source database limits	The tables to be synchronized 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 tables as the objects to be synchronized and you want to edit the tables in the destination database, such as renaming tables or columns, you can synchronize up to 5,000 tables in a single data synchronization task. If you run a task to synchronize more than 5,000 tables, a request error occurs. In this case, we recommend that you configure multiple tasks to synchronize the tables or configure a task to synchronize the entire database. A single data synchronization task can synchronize data from up to 10 databases. If you want to synchronize data from more than 10 databases, we recommend that you configure multiple tasks to synchronize the data. Otherwise, the performance and stability of your data synchronization task may be compromised. DTS uses the fn_log function to obtain logs of the source database. However, this function has performance bottlenecks. Therefore, we recommend that you do not clear the logs of the source database before the task is complete. Otherwise, the task may fail. The following requirements for data logs must be met: The data logging feature must be enabled. The backup mode must be set to Full and full physical backup must be performed. If you perform only incremental data synchronization, the data logs of the source database must be retained for more than 24 hours. If you perform both full data synchronization and incremental data synchronization, the data logs of the source database must be retained for at least seven days. Otherwise, DTS may fail to obtain the data logs and the task may fail. In some cases, data inconsistency or loss may even occur. After full data synchronization is complete, you can set the retention period to more than 24 hours. Make sure that you set the retention period of data logs based on the preceding requirements. Otherwise, the service reliability or performance stated in the service level agreement (SLA) of DTS may not be guaranteed. If CDC needs to be enabled for the tables to be synchronized from the source database, make sure that the tables meet the following requirements. Otherwise, the precheck fails. The value of the srvname field in the sys.sysservers view is the same as the return value of the SERVERPROPERTY function. If the source database is a self-managed SQL Server database, the database owner must be the sa user. If the source database is an ApsaraDB RDS for SQL Server database, the database owner must be the sqlsa user. If the source database is of the Enterprise edition, you must use SQL Server 2008 or later. If the source database is of the Standard edition, you must use SQL Server 2016 SP1 or later. If the source database is of the Standard or Enterprise edition and its version is SQL Server 2017, we recommend that you update the version. If the source database is a read-only instance, you cannot synchronize DDL operations. If the source database is an Azure SQL Database, a data synchronization task can synchronize data from only one database. If the source database is an RDS SQL Server, disable the Transparent Data Encryption (TDE) feature to ensure the stability of a data synchronization task. For more information, see the Disable TDE section in the topic "Configure TDE". In hybrid log-based parsing mode, you cannot perform multiple operations to add columns to or remove columns from the source database within 10 minutes. For example, if you execute the following SQL statements within 10 minutes, an error is reported for the task. `ALTER TABLE test_table DROP COLUMN Flag; ALTER TABLE test_table ADD Remark nvarchar(50) not null default('');` During schema synchronization and full data synchronization, do not execute DDL statements to change the schemas of databases or tables. Otherwise, the data synchronization task fails. If the source database is an ApsaraDB RDS for SQL Server instance that runs SQL Server Web edition, you must set the SQL Server Incremental Synchronization Mode parameter to Incremental Synchronization Based on Logs of Source Database (Heap tables are not supported) when you configure the task. We recommend that you use the `READ_COMMITTED_SNAPSHOT` parameter of transaction processing mode in the source database during full data synchronization. This can prevent the impact of shared lock on data writes. If you do not set the parameter, the exceptions such as inconsistent data and instances that fail to run occur. Issues that arise in such circumstances are not covered by the service level agreement (SLA) of DTS.
Other limits	Only data of basic data types can be synchronized. Data of the CURSOR, ROWVERSION, SQL_VARIANT, HIERARCHYID, POLYGON, GEOMETRY, and GEOGRAPHY types, and user-defined types created using the `CREATE TYPE` command cannot be synchronized. Important The source and destination databases are heterogeneous. The data types that they support do not have one-to-one correspondence. In this case, the task may fail or data loss may occur. We recommend that you evaluate the impact of data type conversion on your business. For more information, see Data type mappings for schema synchronization. You can select only tables as the objects to be synchronized. All tables to be synchronized must be in the same schema. Otherwise, data inconsistency may occur, or the data synchronization task may fail. If you set the SQL Server Incremental Synchronization Mode parameter to Incremental Synchronization Based on Logs of Source Database (Heap tables are not supported) in the Configure Objects step, the tables to be synchronized must have clustered indexes that contain primary key columns. The tables to be synchronized cannot be heap tables, tables without primary keys, compressed tables, or tables with computed columns. Ignore the preceding limits in the hybrid log-based parsing mode. Note For more information about how to view table information, see the How do I view the information about heap tables, tables without primary keys, compressed tables, and tables that contain computed columns in an SQL Server database? section of the FAQ topic. If you set the SQL Server Incremental Synchronization Mode parameter to Log-based Parsing for Non-heap Tables and CDC-based Incremental Synchronization for Heap Tables (Hybrid Log-based Parsing) in the Configure Objects step, take note of the following limits: DTS uses the CDC component to synchronize incremental data. Make sure that the CDC job in the source database runs as expected. Otherwise, the DTS task fails. The CDC component can store the incremental data for 3 days by default. You can adjust the retention period by running the `exec console.sys.sp_cdc_change_job @job_type = 'cleanup', @retention= <time>;` command. Note `<time>` indicates the retention time. Unit: minutes. If the average daily number of the incremental data in the SQL Server database exceeds 10 million, we recommend setting the `<time>` parameter to 1,440. The pre-module of an incremental data migration task in DTS enables database-level and table-level CDC in the source database. In this process, locked tables that lasts a few seconds occurs in the source database due to the limit of SQL Server database. We recommend that you specify a data synchronization task that contains no more than 1,000 tables for which CDC is enabled. Otherwise, the task may be delayed or unstable. If you set the SQL Server Incremental Synchronization Mode parameter to Polling and querying CDC instances for incremental synchronization in the Configure Objects step, the following limits apply: The source database account used by the DTS instance must have the permissions to enable the CDC feature. To enable database-level CDC, you must use an account that is assigned the sysadmin role. To enable table-level CDC, you must use a privileged account. Note A server administrator account of a database in Microsoft Azure SQL Database has the required permissions. CDC can be enabled for all databases that are purchased in Azure SQL Database based on the vCore model. CDC can be enabled for databases that are purchased in Azure SQL Database based on the database transaction unit (DTU) model only if the databases have a service tier of S3 or greater. A privileged account of an Amazon RDS for SQL Server instance has the required permissions. CDC can be enabled for stored procedures at the database level. CDC cannot be enabled for clustered columnstore indexes. The pre-module of an incremental data synchronization task in DTS enables database-level and table-level CDC in the source database. In this process, locked tables that lasts a few seconds occurs in the source database due to the limit of SQL Server database. DTS obtains incremental data by performing round-robin queries on the CDC instance of each table in the source database. Therefore, the number of tables to be migrated from the source database cannot exceed 1,000. Otherwise, the data migration task may be delayed or unstable. The CDC component can store the incremental data for 3 days by default. You can adjust the retention period by running the `exec console.sys.sp_cdc_change_job @job_type = 'cleanup', @retention= <time>;` command. Note `<time>` indicates the retention time. Unit: minutes. If the average daily number of the incremental data in the SQL Server database exceeds 10 million, we recommend setting the `<time>` parameter to 1,440. You cannot execute a DDL statement to add or remove columns more than twice within a minute. Otherwise, the data migration task may fail. During data migration, you cannot modify the CDC instances of the source database. Otherwise, the data migration task may fail or data loss may occur. In Incremental Synchronization Based on Logs of Source Database mode, DTS creates a trigger named dts_cdc_sync_ddl, a heartbeat table named dts_sync_progress, and a DDL history table named dts_cdc_ddl_history in the source database to ensure that the latency of data synchronization is accurate. In hybrid log-based parsing incremental synchronization mode, DTS creates a trigger named dts_cdc_sync_ddl, a heartbeat table named dts_sync_progress, and a DDL history table named dts_cdc_ddl_history and enables CDC for the source database and specific tables. We recommend that you set the maximum number of records per second to 1,000 for the tables for which CDC is enabled in the source database. During initial full data synchronization, concurrent INSERT operations cause table fragmentation in the destination database. Therefore, after initial full data synchronization is complete, the storage space used by the tables in the destination database is larger than that in the source instance. During initial full data synchronization, DTS uses some read and write resources of the source and destination databases, which may increase the database load. Therefore, evaluate the performance of the source and destination databases before you perform data synchronization. We recommend that you perform data synchronization during off-peak hours, for example, when the CPU load of the source and destination databases is below 30%. If the data synchronization task involves incremental data synchronization, DTS does not allow you to perform the reindexing operation. If you perform the reindexing operation, the data synchronization task may fail and data loss may occur. Note DTS cannot synchronize DDL operations related to the primary key of a table for which change data capture (CDC) is enabled. If the number of tables for which CDC is enabled in a data synchronization task is greater than the maximum number of tables for which CDC is enabled that DTS supports, the precheck fails. If the data of a single field that is written to the tables for which CDC is enabled exceeds 64 KB, you must use the `exec sp_configure 'max text repl size', -1;` command to configure the source database. Note By default, the maximum length of a single field in a CDC job that can be processed is 64 KB. When you modify the objects to be synchronized, you cannot remove databases. The incremental data collection modules of multiple data synchronization instances that share a source SQL Server database are independent of each other. 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 DTS 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.
Special cases	If the source instance is an ApsaraDB RDS for SQL Server instance, DTS automatically creates an account named `rdsdt_dtsacct` on the ApsaraDB RDS for SQL Server instance. This account is used for data synchronization. Do not delete this account or change the password of this account when your data synchronization task is running. Otherwise, the task may fail. For more information, see System accounts.

Billing

Synchronization type	Task configuration fee
Schema synchronization and full data synchronization	Free of charge.
Incremental data synchronization	Charged. For more information, see Billing overview.

SQL operations that can be synchronized

Operation type	SQL operation
DML	INSERT, UPDATE, DELETE Note If an UPDATE operation updates only large objects, DTS does not synchronize the operation.

Database account permissions

Database	Required permissions	Account creation and authorization methods
Source self-managed SQL Server	sysadmin permissions.	CREATE USER and User Permission Management.
Destination RDS PostgreSQL instance	The permissions of the destination database owner. The account must be the owner of the database.	Create an account and Create a database.

Preparations

Before you configure a data synchronization task, configure log settings and create clustered indexes on the self-managed SQL Server database.

Important If you need to synchronize data from multiple databases, repeat Steps 1 to 3 for each database. Otherwise, data inconsistency may occur.

Execute the following statement on the self-managed SQL Server database to change the recovery model to full. You can also change the recovery model by using SQL Server Management Studio (SSMS). For more information, see View or Change the Recovery Model of a Database (SQL Server).
```
use master;
GO
ALTER DATABASE <database_name> SET RECOVERY FULL WITH ROLLBACK IMMEDIATE;
GO
```
Parameter:
<database_name>: the name of the source database.
Example:
```
use master;
GO
ALTER DATABASE mytestdata SET RECOVERY FULL WITH ROLLBACK IMMEDIATE;
GO
```
Execute the following statement to create a logical backup for the source database. Skip this step if you have already created a logical backup.
```
BACKUP DATABASE <database_name> TO DISK='<physical_backup_device_name>';
GO
```
Parameter:
- <database_name>: the name of the source database.
- <physical_backup_device_name>: the storage path and file name of the backup file.
Example:
```
BACKUP DATABASE mytestdata TO DISK='D:\backup\dbdata.bak';
GO
```
Execute the following statement to create a log backup for the source database.
```
BACKUP LOG <database_name> to DISK='<physical_backup_device_name>' WITH init;
GO
```
Parameter:
- <database_name>: the name of the source database.
- <physical_backup_device_name>: the storage path and file name of the backup file.
Example:
```
BACKUP LOG mytestdata TO DISK='D:\backup\dblog.bak' WITH init;
GO
```

Procedure

Use one of the following methods to go to the Data Synchronization page and select the region in which the data synchronization instance resides.
DTS console
1. Log on to the DTS console.
2. In the left-side navigation pane, click Data Synchronization.
3. In the upper-left corner of the page, select the region in which the data synchronization task resides.
DMS console
Note
The actual operations 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 and choose DTS (DTS) > Data Synchronization.
3. From the drop-down list to the right of Data Synchronization Tasks, select the region in which the data synchronization instance resides.
Click Create Task to go to the task configuration page.

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

Section	Parameter	Description
N/A	Task Name	The name of the DTS task. DTS automatically generates a task name. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.
Source 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 SQL Server.
	Access Method	Select a connection type based on the deployment location of the source database. In this example, select Self-managed Database on ECS. Note If you select another connection type for the self-managed database, you must also perform the corresponding preparations. For more information, see Preparation overview.
	Instance Region	Select the region where the ECS instance that hosts the source SQL Server database resides.
	ECS Instance ID	Select the ID of the ECS instance that hosts the source SQL Server database.
	Port Number	Enter the service port of the source SQL Server database. The default value is 1433.
	Database Account	Enter the account of the source SQL Server database. For information about the required permissions, see Database account permissions.
	Database Password	The password that is used to access the database.
	Encryption	Select Non-encrypted or SSL-encrypted based on your scenario. If SSL encryption is not enabled for the source database, select Non-encrypted. If the source database has SSL encryption enabled, select SSL-encrypted. DTS trusts the server certificate by default.
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 PostgreSQL.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination RDS PostgreSQL instance resides.
	Instance ID	Select the ID of the destination RDS PostgreSQL instance.
	Database Name	Enter the name of the database that is used to receive data in the destination RDS PostgreSQL instance.
	Database Account	Enter the database account of the destination RDS PostgreSQL instance. For information about the required permissions, see Database account permissions.
	Database Password	The password that is used to access the database.
	Encryption	Specifies whether to encrypt the connection to the source database. You can configure this parameter based on your business requirements. In this example, Non-encrypted is selected. If you want to establish an SSL-encrypted connection to the source database, perform the following steps: Select SSL-encrypted, upload CA Certificate, Client Certificate, and Private Key of Client Certificate as needed, and then specify Private Key Password of Client Certificate. Note If you set Encryption to SSL-encrypted for a self-managed PostgreSQL database, you must upload CA Certificate. If you want to use the client certificate, you must upload Client Certificate and Private Key of Client Certificate and specify Private Key Password of Client Certificate. For information about how to configure SSL encryption for an ApsaraDB RDS for PostgreSQL instance, see SSL encryption.

In the lower part of the page, click Test Connectivity and Proceed. In the CIDR Blocks of DTS Servers dialog box, click Test Connectivity.
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.

Configure the objects to be synchronized.

In the Configure Objects step, configure the objects that you want to synchronize.

Parameter	Description
Synchronization Types	The synchronization types. By default, Incremental Data Synchronization is selected. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of the selected objects from the source database to the destination cluster. The historical data is the basis for subsequent incremental synchronization.
SQL Server Incremental Synchronization Mode	Log-based Parsing for Non-heap Tables and CDC-based Incremental Synchronization for Heap Tables (Hybrid Log-based Parsing): Advantages: This mode supports heap tables, tables without primary keys, compressed tables, and tables with computed columns. This mode provides higher stability and a variety of complete DDL statements. Disadvantages: DTS creates the trigger dts_cdc_sync_ddl, the heartbeat table dts_sync_progress, and the DDL storage table dts_cdc_ddl_history in the source database and enables Change Data Capture (CDC) for the source database and specific tables. You cannot execute the SELECT INTO, TRUNCATE, or RENAME COLUMN statement on tables with CDC enabled in the source database. Triggers created by DTS in the source database cannot be manually deleted. Incremental Synchronization Based on Logs of Source Database (Heap tables are not supported): Advantages: This mode does not modify the settings of the source database. Disadvantages: This mode does not support heap tables, tables without primary keys, compressed tables, or tables with computed columns. Polling and querying CDC instances for incremental synchronization: Advantages: Full data synchronization and incremental data synchronization are supported if the source database is an Amazon RDS for SQL Server instance, a database in Microsoft Azure SQL Database, a Microsoft Azure SQL Managed Instance, a Microsoft Azure SQL Server on Virtual Machine, or a Google Cloud SQL for SQL Server instance. You can use a native CDC component of SQL Server to obtain incremental data. This improves the stability of incremental data synchronization and reduces bandwidth usage. Disadvantages: The account that DTS uses to access the source database must have the permission to enable the CDC feature. Incremental data synchronization has a latency of 10 seconds. If you configure a DTS task to synchronize multiple tables in multiple databases, stability and performance issues may occur.
The maximum number of tables for which CDC is enabled that DTS supports.	Specifies the maximum number of tables for which the current synchronization instance can enable CDC. The default value is 1000. Note This parameter is not available when SQL Server Incremental Synchronization Mode is set to Incremental Synchronization Based on Logs of Source Database (Heap tables are not supported).
Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains tables that have the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck, and the data synchronization task cannot be started. Note If the source and destination databases contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are synchronized to the destination database. For more information, see Map object names. Ignore Errors and Proceed: skips the precheck for identical table 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. If the source and destination databases have the same schema and a data record in the destination database has the same primary key value or unique key value as a data record in the source database: During full data synchronization, DTS does not synchronize the data record to the destination database. The existing data record in the destination database is retained. During incremental data synchronization, DTS synchronizes the data record to the destination database. The existing data record in the destination database is overwritten. If the source and destination databases have different schemas, data may fail to be initialized. In this case, only some columns are synchronized, or the data synchronization instance fails. Proceed with caution.
Capitalization of Object Names in Destination Instance	The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to ensure that the capitalization of object names is consistent with that in the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.
Source Objects	In the Source Objects box, click the table to be synchronized, and then click to move it to the Selected Objects box. Important You can select only tables as the objects to be synchronized. All tables to be synchronized must be in the same schema. Otherwise, data inconsistency may occur, or the data synchronization task may fail.
Selected Objects	By default, the source schema name is used as the destination schema name, and the source table name is used as the destination table name. To modify the name of the schema in the destination RDS PostgreSQL instance, right-click the schema of the table to be synchronized in the Selected Objects section. In the Edit Schema dialog box that appears, modify the Schema Name. Note You can also right-click a table to be synchronized in the Selected Objects section to change the name of the destination table or column, or set WHERE conditions to filter data. For more information, see Specify filter conditions and Map object names. To select SQL operations for incremental synchronization, right-click an object in the Selected Objects section. In the dialog box that appears, select the SQL operations that you want to synchronize. To remove a selected object, click the object in the Selected Objects box, and then click to move it to the Source Objects box.

Click Next: Advanced Settings to configure advanced settings.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules the task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data synchronization instances, 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 synchronization task is started, DTS immediately retries a connection within the time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set this parameter to a value greater than 30. 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 you specify different retry time ranges for multiple data synchronization tasks that have the same source or destination database, the shortest retry time range 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 your earliest opportunity after the source and destination instances are released.
Retry Time for Other Issues	The retry time range for other issues. For example, if the DDL or DML operations fail to be performed after the data synchronization task is started, DTS immediately retries the operations within the time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set this parameter to a value greater than 10. If the failed operations are successfully performed within the specified time range, DTS resumes the data synchronization task. Otherwise, the data synchronization 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 Synchronization	During full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the load on the database servers. You can 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 for full data synchronization tasks to reduce the load on the destination database server. Note You can configure this parameter only if Full Data Synchronization is selected for the Synchronization Types parameter.
Enable Throttling for Incremental Data Synchronization	Specifies whether to enable throttling for incremental data synchronization. You can enable throttling for incremental data synchronization based on your business requirements. To configure throttling, you must configure the RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s) parameters. This reduces the load on the destination database server.
Environment Tag	You can select an environment tag to identify the instance as needed. In this example, you do not need to select a tag.
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 synchronization instance. If the task fails or the synchronization latency exceeds the specified threshold, alert contacts will receive notifications. Valid values: No: does not enable 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 data verification.
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 synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.
- If the data synchronization task fails the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, rerun the precheck.
- 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 issue. Then, run a precheck again.
  If an 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 the instance.

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

On the buy page, configure the Billing Method and Instance Class parameters for the data synchronization task. The following table describes the parameters.

Section	Parameter	Description
New Instance Class	Billing Method	Subscription: You pay for a subscription when you create a data synchronization 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. The pay-as-you-go billing method is suitable for short-term use. If you no longer require a pay-as-you-go data synchronization instance, you can release the instance to reduce costs.
	Resource Group Settings	The resource group to which the data synchronization instance belongs. Default value: default resource group. For more information, see What is Resource Management?
	Instance Class	DTS provides instance classes that vary in synchronization speed. You can select an instance class based on your business requirements. For more information, see Instance classes of data synchronization instances.
	Subscription Duration	If you select the subscription billing method, specify the subscription duration and the number of data synchronization instances that you want to create. The subscription duration can be one to nine months, one year, two years, three years, or five years. Note This parameter is available only if you select the Subscription billing method.

Read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the dialog box that appears, click OK.
You can view the progress of the task in the task list.