This topic describes how to synchronize data from a self-managed Oracle database to a Message Queue for Apache Kafka instance by using Data Transmission Service (DTS).

Prerequisites

  • The source Oracle database and the destination Message Queue for Apache Kafka instance are created.
    Note For more information about the versions supported by the source database and the destination instance, see Overview of data synchronization scenarios.
  • The self-managed Oracle database is running in ARCHIVELOG mode. Archived log files are accessible and a suitable retention period is set for archived log files. For more information, see Managing Archived Redo Log Files.
  • Supplemental logging, including SUPPLEMENTAL_LOG_DATA_PK and SUPPLEMENTAL_LOG_DATA_UI, is enabled for the self-managed Oracle database. For more information, see Supplemental Logging.
  • The available storage space of the destination Message Queue for Apache Kafka instance is larger than the total size of the data in the self-managed Oracle database.
  • In the destination Message Queue for Apache Kafka instance, a topic is created to receive the synchronized data. For more information, see Step 1: Create a topic.

Limits

Category Description
Limits on the source database
  • Requirements for the objects to be synchronized:
    • 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 the version of your Oracle database is 12c or later, the names of the tables to be synchronized cannot exceed 30 bytes in length.
    • If you select tables as the objects to be synchronized and you want to edit tables (such as renaming tables or columns), up to 1,000 tables can be synchronized in a single data synchronization task. If you run a task to synchronize more than 1,000 tables, a request error occurs. In this case, we recommend that you split the tables, configure multiple tasks to synchronize the tables, or configure a task to synchronize the entire database.
  • If the source database is an Oracle Real Application Cluster (RAC) database connected over Express Connect, you must specify a virtual IP address (VIP) for the database when you configure the data synchronization task.
  • If the self-managed Oracle database is an Oracle RAC database, you can only use a VIP rather than a Single Client Access Name (SCAN) IP address when you configure the data synchronization task. After you specify the VIP, node failover of the Oracle RAC database is not supported.
  • The following requirements must be met:
    • The redo logging and archive logging features must be enabled.

    • If you perform only incremental data synchronization, the redo logs and archive logs of the source database must be stored for more than 24 hours. If you perform both full data and incremental data synchronization, the redo logs and archive logs of the source database must be stored for at least seven days. After full data synchronization is completed, you can set the retention period to more than 24 hours. Otherwise, DTS may fail to obtain the redo logs and archive logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. Make sure that you set the retention period of redo logs and archive logs in accordance with the preceding requirements. Otherwise, the Service Level Agreement (SLA) of DTS does not ensure service reliability and performance.

  • If you perform a primary/secondary switchover on the source database when the data synchronization task is running, the task fails.
Other limits
  • DTS does not synchronize the data in a renamed table to the destination Kafka cluster. This applies if the new table name is not included in the objects to be synchronized. To synchronize the data in a renamed table to the destination Kafka cluster, you must reselect the objects to be synchronized. For more information, see Add an object to a data synchronization task.
  • Before you synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. During full data synchronization, DTS uses read and write resources of the source and destination databases. This may increase the loads of the database servers.
  • During full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination database. After full data synchronization is completed, the tablespace of the destination database is larger than that of the source database.
  • We recommend that you do not use gh-ost or pt-online-schema-change to perform DDL operations on objects. Otherwise, data synchronization may fail.
  • DTS calculates synchronization latency based on the timestamp of the latest synchronized data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for a long time, the synchronization latency may be inaccurate. If the latency of the synchronization task is too high, you can perform a DML operation on the source database to update the latency.
    Note If you select an entire database as the object to be synchronized, you can create a heartbeat table. The heartbeat table is updated or receives data every second.
  • During data synchronization, we recommend that you use only DTS to write data to the destination database. This prevents data inconsistency between the source and destination databases. For example, if you use tools other than DTS to write data to the destination database, data loss may occur in the destination database when you use Data Management (DMS) to perform online DDL operations.

Billing

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

Size limit of a single record

The size of a single record written to Kafka is 10 MB. Therefore, if a row of source data exceeds 10 MB, the task will be interrupted because DTS cannot write data to Kafka. In this scenario, we recommend that you do not synchronize the tables that contain large fields. You can synchronize only some columns. When you configure the DTS task, you must exclude the records of these large fields. If tables that contain large fields are included in the objetcs of the task, you must remove the tables, add the tables to the objects again, and then set filter conditions to exclude the large field columns.

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
For more information, see Synchronization topologies.

SQL operations that can be synchronized

Operation type SQL statements
DML INSERT, UPDATE, and DELETE
DDL
  • CREATE TABLE, ALTER TABLE, DROP TABLE, RENAME TABLE, and TRUNCATE TABLE
  • CREATE VIEW, ALTER VIEW, and DROP VIEW
  • CREATE PROCEDURE, ALTER PROCEDURE, and DROP PROCEDURE
  • CREATE FUNCTION, DROP FUNCTION, CREATE TRIGGER, and DROP TRIGGER
  • CREATE INDEX and DROP INDEX

Permissions required for database accounts

Database Required permissions References
Self-managed Oracle database Database administrator (DBA) CREATE USER and GRANT
Notice If you need to synchronize data from an Oracle database but the database administrator (DBA) permission cannot be granted to the database account, you can enable archive logging and supplemental logging, and grant fine-grained permissions to the account.
  1. Enable archive logging and supplemental logging.
    Type Procedure
    Archive logging Execute the following statements to enable archive logging:
    shutdown immediate;
startup mount;
alter database archivelog;
alter database open;
archive log list;
    Supplemental logging Enable supplemental logging at the database or table level:
    Note You can enable database-level supplemental logging to ensure the stability of DTS tasks. You can enable table-level supplemental logging to reduce the disk usage of the source Oracle database.
    • Enable database-level supplemental logging
      1. Enable minimal supplemental logging:
        alter database add supplemental log data;
      2. Enable primary key and unique key supplemental logging at the database level:
        alter database add supplemental log data (primary key,unique index) columns;
    • Enable table-level supplemental logging
      1. Enable minimal supplemental logging:
        alter database add supplemental log data;
      2. Enable table-level supplemental logging by using one of the following methods:
        • Enable primary key supplemental logging at the table level:
          alter table table_name add supplemental log data (primary key) columns;
        • Enable table-level supplemental logging for all columns:
          alter table tb_name add supplemental log data (all) columns ;
  2. Grant fine-grained permissions to an Oracle database account 
    # Create a database account, for example, rdsdt_dtsacct, and grant permissions to the account.
create user rdsdt_dtsacct IDENTIFIED BY rdsdt_dtsacct;
grant create session to rdsdt_dtsacct;
grant connect to rdsdt_dtsacct;
grant resource to rdsdt_dtsacct;
grant execute on sys.dbms_logmnr to rdsdt_dtsacct;
grant select on V_$LOGMNR_LOGS to rdsdt_dtsacct;
grant select on  all_objects to rdsdt_dtsacct;
grant select on  all_tab_cols to rdsdt_dtsacct;
grant select on  dba_registry to rdsdt_dtsacct;
grant select any table to rdsdt_dtsacct;
grant select any transaction to rdsdt_dtsacct;
-- v$log privileges
grant select on v_$log to rdsdt_dtsacct;
-- v$logfile privileges
grant select on v_$logfile to rdsdt_dtsacct;
-- v$archived_log privileges
grant select on v_$archived_log to rdsdt_dtsacct;
-- v$parameter privileges
grant select on v_$parameter to rdsdt_dtsacct;
-- v$database privileges
grant select on v_$database to rdsdt_dtsacct;
-- v$active_instances privileges
grant select on v_$active_instances to rdsdt_dtsacct;
-- v$instance privileges
grant select on v_$instance to rdsdt_dtsacct;
-- v$logmnr_contents privileges
grant select on v_$logmnr_contents to rdsdt_dtsacct;
-- system tables
grant select on sys.USER$ to rdsdt_dtsacct;
grant select on SYS.OBJ$ to rdsdt_dtsacct;
grant select on SYS.COL$ to rdsdt_dtsacct;
grant select on SYS.IND$ to rdsdt_dtsacct;
grant select on SYS.ICOL$ to rdsdt_dtsacct;
grant select on SYS.CDEF$ to rdsdt_dtsacct;
grant select on SYS.CCOL$ to rdsdt_dtsacct;
grant select on SYS.TABPART$ to rdsdt_dtsacct;
grant select on SYS.TABSUBPART$ to rdsdt_dtsacct;
grant select on SYS.TABCOMPART$ to rdsdt_dtsacct;
grant select on v$database to rdsdt_dtsacct;
grant select on dba_objects to rdsdt_dtsacct;
grant select on DBA_TAB_COMMENTS to rdsdt_dtsacct;
grant select on dba_tab_cols to rdsdt_dtsacct;
    # Switch to the pluggable database (PDB). Create a database account, for example, rdsdt_dtsacct, and grant permissions to the account.
ALTER SESSION SET container = ORCLPDB1;
create user rdsdt_dtsacct IDENTIFIED BY rdsdt_dtsacct;
grant create  session to rdsdt_dtsacct;
grant connect  to rdsdt_dtsacct;
grant resource to rdsdt_dtsacct;
grant execute on sys.dbms_logmnr to rdsdt_dtsacct;
grant select on  all_objects to rdsdt_dtsacct;
grant select on  all_tab_cols to rdsdt_dtsacct;
grant select on  dba_registry to rdsdt_dtsacct;
grant select any table to rdsdt_dtsacct;
grant select any transaction to rdsdt_dtsacct;
-- v$log privileges
grant select on v_$log to rdsdt_dtsacct;
-- v$logfile privileges
grant select on v_$logfile to rdsdt_dtsacct;
-- v$archived_log privileges
grant select on v_$archived_log to rdsdt_dtsacct;
-- v$parameter privileges
grant select on v_$parameter to rdsdt_dtsacct;
-- v$database privileges
grant select on v_$database to rdsdt_dtsacct;
-- v$active_instances privileges
grant select on v_$active_instances to rdsdt_dtsacct;
-- v$instance privileges
grant select on v_$instance to rdsdt_dtsacct;
-- v$logmnr_contents privileges
grant select on v_$logmnr_contents to rdsdt_dtsacct;
grant select on sys.USER$ to rdsdt_dtsacct;
grant select on SYS.OBJ$ to rdsdt_dtsacct;
grant select on SYS.COL$ to rdsdt_dtsacct;
grant select on SYS.IND$ to rdsdt_dtsacct;
grant select on SYS.ICOL$ to rdsdt_dtsacct;
grant select on SYS.CDEF$ to rdsdt_dtsacct;
grant select on SYS.CCOL$ to rdsdt_dtsacct;
grant select on SYS.TABPART$ to rdsdt_dtsacct;
grant select on SYS.TABSUBPART$ to rdsdt_dtsacct;
grant select on SYS.TABCOMPART$ to rdsdt_dtsacct;
-- V$PDBS privileges
grant select on V_$PDBS to rdsdt_dtsacct;
grant select on v$database to rdsdt_dtsacct;
grant select on dba_objects to rdsdt_dtsacct;
grant select on DBA_TAB_COMMENTS to rdsdt_dtsacct;
grant select on dba_tab_cols to rdsdt_dtsacct;

# Switch to the container database (CDB). Create a database account and grant permissions to the account by using one of the following methods:
ALTER SESSION SET container = CDB$ROOT;
Method 1: Create a global account starting with C##, for example, C##rdsdt_dtsacct, and grant permissions to the account. If you use this method, you must submit a ticket and contact the DTS team to modify some parameters. The link to submit a ticket is provided in the note.
create user C##rdsdt_dtsacct IDENTIFIED BY rdsdt_dtsacct;
grant create session to C##rdsdt_dtsacct;
grant connect to C##rdsdt_dtsacct;
grant resource to C##rdsdt_dtsacct;
grant select on v_$logmnr_contents to rdsdt_dtsacct;
grant LOGMINING to C##rdsdt_dtsacct;
grant EXECUTE_CATALOG_ROLE to C##rdsdt_dtsacct;
grant execute on sys.dbms_logmnr to C##rdsdt_dtsacct;
grant select on v$database to rdsdt_dtsacct;
grant select on dba_objects to rdsdt_dtsacct;
grant select on DBA_TAB_COMMENTS to rdsdt_dtsacct;
grant select on dba_tab_cols to rdsdt_dtsacct;
Method 2: Create a database account, for example, rdsdt_dtsacct, and grant permissions to the account. If you use this method, you must modify the default parameters of the Oracle database.
alter session set "_ORACLE_SCRIPT"=true;
create user rdsdt_dtsacct IDENTIFIED BY rdsdt_dtsacct;
grant create session to rdsdt_dtsacct;
grant connect to rdsdt_dtsacct;
grant select on v_$logmnr_contents to rdsdt_dtsacct;
grant LOGMINING TO rdsdt_dtsacct;
grant EXECUTE_CATALOG_ROLE to rdsdt_dtsacct;
grant execute on sys.dbms_logmnr to rdsdt_dtsacct;
grant select on v$database to rdsdt_dtsacct;
grant select on dba_objects to rdsdt_dtsacct;
grant select on DBA_TAB_COMMENTS to rdsdt_dtsacct;
grant select on dba_tab_cols to rdsdt_dtsacct;
    # Create a database account, for example, rdsdt_dtsacct, and grant permissions to the account.
create user rdsdt_dtsacct IDENTIFIED BY rdsdt_dtsacct;
grant create  session to rdsdt_dtsacct;
grant connect  to rdsdt_dtsacct;
grant resource to rdsdt_dtsacct;
grant select on V_$LOGMNR_LOGS to rdsdt_dtsacct;
grant select on  all_objects to rdsdt_dtsacct;
grant select on  all_tab_cols to rdsdt_dtsacct;
grant select on  dba_registry to rdsdt_dtsacct;
grant select any table to rdsdt_dtsacct;
grant select any transaction to rdsdt_dtsacct;
-- v$log privileges
grant select on v_$log to rdsdt_dtsacct;
-- v$logfile privileges
grant select on v_$logfile to rdsdt_dtsacct;
-- v$archived_log privileges
grant select on v_$archived_log to rdsdt_dtsacct;
-- v$parameter privileges
grant select on v_$parameter to rdsdt_dtsacct;
-- v$database privileges
grant select on v_$database to rdsdt_dtsacct;
-- v$active_instances privileges
grant select on v_$active_instances to rdsdt_dtsacct;
-- v$instance privileges
grant select on v_$instance to rdsdt_dtsacct;
-- v$logmnr_contents privileges
grant select on v_$logmnr_contents to rdsdt_dtsacct;
grant select on sys.USER$ to rdsdt_dtsacct;
grant select on SYS.OBJ$ to rdsdt_dtsacct;
grant select on SYS.COL$ to rdsdt_dtsacct;
grant select on SYS.IND$ to rdsdt_dtsacct;
grant select on SYS.ICOL$ to rdsdt_dtsacct;
grant select on SYS.CDEF$ to rdsdt_dtsacct;
grant select on SYS.CCOL$ to rdsdt_dtsacct;
grant select on SYS.TABPART$ to rdsdt_dtsacct;
grant select on SYS.TABSUBPART$ to rdsdt_dtsacct;
grant select on SYS.TABCOMPART$ to rdsdt_dtsacct;
grant LOGMINING TO rdsdt_dtsacct;
grant EXECUTE_CATALOG_ROLE to rdsdt_dtsacct;
grant execute on sys.dbms_logmnr to rdsdt_dtsacct;
grant select on v$database to rdsdt_dtsacct;
grant select on dba_objects to rdsdt_dtsacct;
grant select on DBA_TAB_COMMENTS to rdsdt_dtsacct;
grant select on dba_tab_cols to rdsdt_dtsacct;
    Note To create a global account starting with C## for a multitenant CDB$ROOT in Oracle 12c to 19c, you must submit a ticket and contact the DTS team to modify some parameters.

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.
    Region
  3. Click Create Task. On the page that appears, configure the source and destination databases.
    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 Oracle.
    Access Method Select an instance type based on the deployment of the source database. In this example, select Self-managed Database on ECS.
    Note If your source database is a self-managed database, you must deploy the network environment for the database. For more information, see Preparation overview.
    Instance Region Select the region where the self-managed Oracle database resides.
    ECS Instance ID Select the ID of the Elastic Compute Service (ECS) instance that hosts the self-managed Oracle database.
    Port Number Enter the service port number of the self-managed Oracle database. The default port number is 1521.
    Oracle Type
    • If you select Non-RAC Instance, you must specify the SID parameter.
    • If you select RAC or PDB Instance, you must specify the Service Name parameter.
      Notice RAC instances are not supported.
    In this example, select Non-RAC Instance.
    Database Account Enter the account of the self-managed Oracle database. For information about the permissions that are required for the account, see Permissions required for database accounts.
    Database Password

    The password of the database account.

    Destination Database Database Type Select Kafka.
    Access Method Select Express Connect, VPN Gateway, or Smart Access Gateway.
    Note You cannot select Message Queue for Apache Kafka as the instance type. You can use Message Queue for Apache Kafka as a self-managed Kafka database to configure data synchronization.
    Instance Region Select the region where the destination Message Queue for Apache Kafka instance resides.
    Connected VPC Select the ID of the virtual private cloud (VPC) to which the destination Message Queue for Apache Kafka instance belongs. To obtain the VPC ID, you can log on to the Message Queue for Apache Kafka console and go to the Instance Details page of the Message Queue for Apache Kafka instance. In the Basic Information section, you can view the VPC ID.
    Hostname or IP Address Enter an IP address that is included in the Default Endpoint parameter of the Message Queue for Apache Kafka instance.
    Note To obtain an IP address, you can log on to the Message Queue for Apache Kafka console and go to the Instance Details page of the Message Queue for Apache Kafka instance. In the Basic Information section, you can obtain an IP address from the Default Endpoint parameter.
    Port Number Enter the service port number of the Message Queue for Apache Kafka instance. The default port number is 9092.
    Database Account Enter the database account of the Message Queue for Apache Kafka instance.
    Note If the instance type of the Message Queue for Apache Kafka instance is VPC Instance, you do not need to specify the database account or database password.
    Database Password

    The password of the database account.

    Kafka Version Select the version of the Message Queue for Apache Kafka instance.
    Encryption Select Non-encrypted or SCRAM-SHA-256 based on your business and security requirements.
    Topic Select a topic from the drop-down list.
    Topic That Stores DDL Information Select a topic from the drop-down list. The topic is used to store the DDL information. If you do not specify this parameter, the DDL information is stored in the topic that is specified by the Topic parameter.
    Whether to Use Kafka Schema Registry Kafka Schema Registry provides a serving layer for your metadata. It provides a RESTful interface for storing and retrieving your Avro schemas.
    • No: Kafka Schema Registry is not used.
    • Yes: Kafka Schema Registry is used. In this case, you must enter the URL or IP address that is registered in Kafka Schema Registry for your Avro schemas.
  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 SettingsBasic 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.

      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 identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data synchronization task cannot be started.

        Note You can use the object name mapping feature to rename the tables that are migrated to the destination database. You can use this feature if the source and destination databases contain identical table names and the tables 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 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 has the same primary key as an existing data record in the destination 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, initial data synchronization may fail. In this case, only part of the columns are synchronized, or the data synchronization task fails.
      Data Format in Kafka Select the format in which data records are stored in the Message Queue for Apache Kafka instance.
      • If you select DTS Avro, data is parsed based on the schema definition of DTS Avro. For more information, see DTS Avro schema.
      • If you select SharePlex JSON, data is stored in the SharePlex JSON format. For more information, see Shareplex JSON.
      Policy for Shipping Data to Kafka Partitions Select a synchronization policy based on your business requirements. For more information, see Specify the policy for migrating data to Kafka partitions.
      Select Objects

      Select one or more objects from the Source Objects section and click the Rightwards arrow icon to add the objects to the Selected Objects section.

      Note You can select columns, tables, or databases as objects to synchronize. If you select tables or columns as the objects to synchronize, DTS does not synchronize other objects such as views, triggers, and stored procedures to the destination database.
      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 DML and DDL operations that you want to synchronize. For more information, see SQL operations that can be synchronized.
    • Advanced SettingsAdvanced 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, table names, and column 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 Info icon 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.