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Synchronize self-managed PostgreSQL to PolarDB for PostgreSQL (Compatible with Oracle)

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You can use Data Transmission Service (DTS) to synchronize data from a self-managed PostgreSQL database to PolarDB for PostgreSQL (Compatible with Oracle).

Prerequisites

  • You have a source self-managed PostgreSQL database and a destination PolarDB for PostgreSQL (Compatible with Oracle) cluster.

    Note

  • The destination PolarDB for PostgreSQL (Compatible with Oracle) cluster must have more storage space than the source self-managed PostgreSQL database.

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 constraint checks and foreign key cascade operations at the session level. Data inconsistency may occur if cascade update or delete operations are performed on the source database while the task is running.

Type

Description

Source database limits

  • The tables to be synchronized must have primary keys or UNIQUE constraints, and the fields must be unique. Otherwise, duplicate data may exist in the destination database.

    Note

    If the destination table is not created by DTS (that is, Synchronization Types is not set to Schema Synchronization), you must ensure that the table has the same primary key or non-null UNIQUE constraint as the source table. Otherwise, duplicate data may occur in the destination database.

  • If you synchronize data at the table level and need to edit objects, such as mapping column names, and the number of tables in a single synchronization task exceeds 5,000, split the tables into multiple tasks or configure a task to synchronize the entire database. Otherwise, a request error may be reported after you submit the task.

  • The name of the database to be synchronized cannot contain hyphens (-), such as dts-testdata.

  • Write-ahead log (WAL):

    • WAL must be enabled. Set the wal_level parameter to logical.

    • For an incremental synchronization task, DTS requires that the WAL logs in the source database are retained for more than 24 hours. For a task that performs both full and incremental synchronization, DTS requires that the WAL logs are retained for at least 7 days. You can change the log retention period to more than 24 hours after the initial full data synchronization is complete. If the task fails because DTS cannot obtain the required WAL logs, or in extreme cases, data inconsistency or data loss occurs, the issue is not covered by the DTS Service-Level Agreement (SLA) because the specified log retention period is shorter than required.

  • If a failover occurs on the self-managed PostgreSQL database, the synchronization fails.

  • Make sure that the values of the max_wal_senders and max_replication_slots parameters are greater than the sum of the number of replication slots in use and the number of DTS instances to be created with this self-managed PostgreSQL database as the source.

  • If the source database has long-running transactions and the instance includes an incremental synchronization task, the write-ahead logs (WALs) generated before the long-running transactions are committed cannot be cleared and may accumulate. This can cause the disk space of the source database to become insufficient.

  • When the source instance is Google Cloud Platform Cloud SQL for PostgreSQL, the Database Account for the source database must have the `cloudsqlsuperuser` permission. When you select synchronization objects, you must select objects that this account is authorized to manage, or grant the Owner permission for the objects to be synchronized to this account (for example, by running the GRANT <owner_of_the_object_to_be_synchronized> TO <source_database_account_used_by_the_task> command to allow this account to perform related operations as the object owner).

    Note

    An account with the cloudsqlsuperuser permission cannot manage data whose owner is another account with the cloudsqlsuperuser permission.

  • Due to the limits of logical subscription in the source database, if a single piece of data to be synchronized exceeds 256 MB after an incremental change, the synchronization instance may fail and cannot be recovered. You must reconfigure the synchronization instance.

  • Do not run DDL operations that change database or table schemas during schema synchronization or full synchronization. Otherwise, the synchronization task fails.

    Note

    During full synchronization, DTS queries the source database. This creates metadata locks that may block DDL operations on the source database.

  • If you perform a major engine version upgrade on the source database while the synchronization instance is running, the instance fails and cannot be recovered. You must reconfigure the synchronization instance.

Other limits

  • For full or incremental synchronization tasks where the tables to be synchronized in the source database contain foreign keys, triggers, or event triggers, DTS temporarily sets the session_replication_role parameter to replica at the session level if the destination database account is a privileged account. If the destination database account does not have this permission, you need to manually set the session_replication_role parameter to replica in the destination database. During this period (while the session_replication_role parameter is set to replica), if cascading update or delete operations occur in the source database, data inconsistency may occur. After the DTS synchronization task is released, you can change the session_replication_role parameter value back to origin.

  • If a table to be synchronized contains a SERIAL field, the source database automatically creates a Sequence for the field. Therefore, when you configure Source Objects, if you select Schema Synchronization for Synchronization Types, we recommend that you also select Sequence or synchronize the entire schema. Otherwise, the synchronization instance may fail.

  • A single data synchronization task can synchronize only one database. To synchronize multiple databases, you must configure a data synchronization task for each database.

  • DTS does not synchronize TimescaleDB extension tables, tables with cross-schema inheritance, or tables that contain expression-based unique indexes.

  • In the following three scenarios, you must run the ALTER TABLE schema.table REPLICA IDENTITY FULL; command on the tables to be synchronized before you write data to them. This ensures data consistency. Do not perform table locking operations during the execution of this command. Otherwise, the tables may be locked. If you skip the related check items in the precheck, DTS automatically runs this command during the initialization of the instance.

    • When the instance runs for the first time.

    • When the synchronization granularity is schema, and a new table is created in the schema to be synchronized or a table to be synchronized is rebuilt using the RENAME command.

    • When you use the Modify Objects feature.

    Note

    • In the command, replace schema and table with the names of the schema and table to which the data to be synchronized belongs.

    • Perform this operation during off-peak hours.

  • DTS validates data content but does not validate metadata such as sequences. You must validate the metadata yourself.

  • After the business is switched to the destination, new sequences do not use the maximum sequence value from the source database as the initial value for incrementing. You must update the sequence value of the destination database before the business switchover. For more information, see Update the sequence value of the destination database.

  • DTS creates the following temporary tables in the source database to obtain the DDL statements of incremental data, the structure of incremental tables, and heartbeat information. During synchronization, do not delete these temporary tables. Otherwise, the DTS task becomes abnormal. The temporary tables are automatically deleted after the DTS instance is released.

    public.dts_pg_class, public.dts_pg_attribute, public.dts_pg_type, public.dts_pg_enum, public.dts_postgres_heartbeat, public.dts_ddl_command, public.dts_args_session, and public.aliyun_dts_instance.

  • To ensure the accuracy of the displayed synchronization latency, DTS adds a heartbeat table named dts_postgres_heartbeat to the source database.

  • During data synchronization, DTS creates a replication slot with the prefix dts_sync_ in the source database to replicate data. DTS uses this replication slot to obtain incremental logs from the source database within 15 minutes. When the data synchronization fails or the synchronization instance is released, DTS attempts to automatically clear this replication slot.

    Note

    • If you change the password of the database account used by the task or delete the DTS IP address whitelist from the source database during data synchronization, the replication slot cannot be automatically cleared. In this case, you must manually clear the replication slot in the source database to prevent it from accumulating and occupying disk space, which can make the source database unavailable.

    • If a failover occurs on the source database, you must log on to the secondary database to manually clear the replication slot.

    Amazon slot查询信息

  • Evaluate the performance of the source and destination databases before you synchronize data. Synchronize data during off-peak hours. Otherwise, initial full data synchronization consumes read and write resources on the source and destination databases, which may increase the database load.

  • Initial full data synchronization runs concurrent INSERT operations, which causes table fragmentation in the destination database. As a result, the tablespace of the destination instance is larger than that of the source instance after the initial full data synchronization is complete.

  • For table-level data synchronization, if no data other than the data from DTS is written to the destination database, you can use Data Management (DMS) to perform online DDL operations. For more information, see Perform schema changes without table locks.

  • During DTS synchronization, do not write data other than the data from DTS to the destination database. Otherwise, data inconsistency occurs between the source and destination databases. For example, if you use DMS to perform online DDL operations while other data is being written to the destination database, data may be lost in the destination database.

  • If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters.

    Note

    Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.

  • When you synchronize partitioned tables, you must include both the parent table and its child tables as synchronization objects. Otherwise, data inconsistency may occur in the partitioned table.

    Note

    The parent table of a PostgreSQL partitioned table does not directly store data. All data is stored in the child tables. The synchronization task must include the parent table and all its child tables. Otherwise, data in the child tables may not be synchronized, leading to data inconsistency between the source and destination.

Billing

Synchronization type

Link configuration fees

Schema synchronization and full data synchronization

Free of charge.

Incremental synchronization

Charged. For more information, see Billing overview.

Synchronization topologies

  • One-way one-to-one synchronization

  • One-way one-to-many synchronization

  • One-way cascade synchronization

  • One-way many-to-one synchronization

For more information about synchronization topologies, see Synchronization topologies.

Supported objects

  • SCHEMA and TABLE.

    Note

    This includes PRIMARY KEY, UNIQUE KEY, FOREIGN KEY, DATATYPE (built-in data types), and DEFAULT CONSTRAINT.

  • VIEW, PROCEDURE (for PostgreSQL 11 or later), FUNCTION, RULE, SEQUENCE, EXTENSION, TRIGGER, AGGREGATE, INDEX, OPERATOR, and DOMAIN.

Supported SQL operations

Operation type

SQL operations

DML

INSERT, UPDATE, and DELETE

DDL

  • Only data synchronization tasks created after October 1, 2020 (UTC+8)October 1, 2020 (Singapore Time) support DDL operation synchronization.

    Important

    • For sync tasks created before September 9, 2022 (UTC+8), create triggers and functions in the source database to catch DDL information before configuring the sync task. For more information, see DDL incremental migration for PostgreSQL using triggers and functions.

    • Data of the BIT type cannot be synchronized during incremental data synchronization.

  • The sync task supports the following DDL statements. The database account for the source database must be a privileged account, and the minor version of the self-managed PostgreSQL instance must be 20210228 or later.

    • CREATE TABLE and DROP TABLE

    • ALTER TABLE (including RENAME TABLE, ADD COLUMN, ADD COLUMN DEFAULT, ALTER COLUMN TYPE, DROP COLUMN, ADD CONSTRAINT, ADD CONSTRAINT CHECK, and ALTER COLUMN DROP DEFAULT)

    • TRUNCATE TABLE (for source PostgreSQL 11 or later)

    • CREATE INDEX ON TABLE

    Important

    • Synchronization of additional information in DDL statements, such as CASCADE or RESTRICT, is not supported.

    • Synchronization of DDL statements in sessions that use the SET session_replication_role = replica command is not supported.

    • Synchronization of DDL that is executed by methods such as invoking FUNCTION is not supported.

    • If a single transaction in the source database contains both DML and DDL statements, the DDL statements are not synchronized.

    • If a single transaction in the source database contains DDL statements for objects that are not synchronized, the DDL statements are not synchronized.

    • Synchronization of DDL statements that are executed directly within a plugin using the Server Programming Interface (SPI) is not supported.

Permission requirements for database accounts

Database

Required permissions

Account creation and authorization methods

Self-managed PostgreSQL

Superuser permissions.

CREATE USER and GRANT.

PolarDB for PostgreSQL (Compatible with Oracle)

Database owner permission.

Create a database account.

Note

The database owner is specified when the database is created.

Preparation

Note

The following steps apply to Linux.

Complete the following steps for all versions of self-hosted PostgreSQL.

  1. Log in to the server that hosts your self-hosted PostgreSQL.

  2. Run the following command to check the number of current replication slots:

    select count(1) from pg_replication_slots;

  3. Modify the postgresql.conf configuration file. Set the wal_level parameter to logical, and ensure that the values for the max_wal_senders and max_replication_slots parameters exceed the sum of the current number of replication slots and the number of DTS instances you plan to create.

    # - Settings -

wal_level = logical			# minimal, replica, or logical
					# (change requires restart)

......

# - Sending Server(s) -

# Set these on the master and on any standby that will send replication data.

max_wal_senders = 10		# max number of walsender processes
				# (change requires restart)
#wal_keep_segments = 0		# in logfile segments, 16MB each; 0 disables
#wal_sender_timeout = 60s	# in milliseconds; 0 disables

max_replication_slots = 10	# max number of replication slots
				# (change requires restart)
    Note

    After modifying the configuration file, restart the self-hosted PostgreSQL database for the changes to take effect.

  4. Add the DTS IP addresses to the pg_hba.conf configuration file for your self-hosted PostgreSQL. Add only the DTS IP CIDR blocks for the region where the destination database is located. For more information, see Add DTS server IP addresses to a whitelist.

    Note

    • After you modify the configuration file, you must either run the SELECT pg_reload_conf(); command or restart the self-hosted PostgreSQL database to apply the changes.

    • For details on configuring this file, see The pg_hba.conf file. If you have already configured the trusted address as 0.0.0.0/0 (as shown in the figure below), you can skip this step.

    IP

  5. In the destination database instance, create the databases and schemas that correspond to the objects you plan to synchronize.

If your self-hosted PostgreSQL version is 9.4.8 to 10.0, you must also complete the following steps.

  1. Download, compile, and install the PostgreSQL source code.

    1. Log in to the server that hosts your self-hosted PostgreSQL.

    2. Download the source code that corresponds to your PostgreSQL version from the PostgreSQL official website.

    3. Run sudo ./configure, sudo make, and sudo make install in sequence.

      Important

      • When you compile and install PostgreSQL, the operating system version must match the GCC (GNU Compiler Collection) version.

      • If you encounter an error when you run sudo ./configure, adjust the command based on the error message. For example, if the error message is readline library not found. Use --without-readline to disable readline support., run sudo ./configure --without-readline instead.

      • If you install PostgreSQL by using other methods, you must compile ali_decoding in a test environment where the operating system version and GCC version match those of your production environment.

  2. Download, compile, and install the DTS ali_decoding plugin.

    1. Download ali_decoding.

    2. Copy the entire ali_decoding directory to the contrib directory of your compiled PostgreSQL installation.

      contrib目录

    3. Navigate to the ali_decoding directory and replace the content of the Makefile with the following:

      # contrib/ali_decoding/Makefile
MODULE_big = ali_decoding
MODULES = ali_decoding
OBJS    = ali_decoding.o

DATA = ali_decoding--0.0.1.sql ali_decoding--unpackaged--0.0.1.sql

EXTENSION = ali_decoding

NAME = ali_decoding

#subdir = contrib/ali_decoding
#top_builddir = ../..
#include $(top_builddir)/src/Makefile.global
#include $(top_srcdir)/contrib/contrib-global.mk

#PG_CONFIG = /usr/pgsql-9.6/bin/pg_config
#pgsql_lib_dir := $(shell $(PG_CONFIG) --libdir)
#PGXS := $(shell $(PG_CONFIG) --pgxs)
#include $(PGXS)

# Use the following for source code installation
ifdef USE_PGXS
PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)
include $(PGXS)
else
subdir = contrib/ali_decoding
top_builddir = ../..
include $(top_builddir)/src/Makefile.global
include $(top_srcdir)/contrib/contrib-global.mk
endif

    4. In the ali_decoding directory, run sudo make and then sudo make install.

    5. Copy the following files to their specified locations.

      指定位置

  3. In the destination database instance, create the databases and schemas that correspond to the objects you plan to synchronize.

Procedure

  1. Go to the data synchronization task list page in the destination region. You can do this in one of two ways.

    DTS console

    1. Log on to the DTS console.

    2. In the navigation pane on the left, click Data Synchronization.

    3. In the upper-left corner of the page, select the region where the synchronization instance is located.

    DMS console

    Note

    The actual steps may vary depending on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.

    1. Log on to the DMS console.

    2. In the top menu bar, choose Data + AI > DTS (DTS) > Data Synchronization.

    3. To the right of Data Synchronization Tasks, select the region of the synchronization instance.

  2. Click Create Task to open the task configuration page.

  3. Configure the source and destination databases.

    Category

    Parameter

    Description

    N/A

    Task Name

    DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.

    Source Database

    Select Existing Connection

    • Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured.

      Note

      In the DMS console, this configuration item is Select a DMS database instance.

    • If you have not registered the database instance or do not need to use a registered instance, manually configure the database information below.

    Database Type

    Select PostgreSQL.

    Connection Type

    Select Cloud Enterprise Network (CEN).

    Instance Region

    Select the region where the self-managed PostgreSQL database resides.

    Cross-account

    If you synchronize data within the same Alibaba Cloud account, select No.

    Connected VPC

    Select the VPC that is connected to the self-managed PostgreSQL database.

    IP address

    Enter the server IP address of the self-managed PostgreSQL database.

    Port

    Enter the port number used by the self-managed PostgreSQL database. The default value is 5432.

    Database Name

    Enter the name of the database that contains the objects to be synchronized.

    Database Account

    Enter the database account for the self-managed PostgreSQL database. For information about the required permissions, see Database account permissions.

    Database Password

    Enter the password for the specified database account.

    Encryption

    Select a connection method based on your requirements. In this example, Non-encrypted is selected.

    To connect to the database using SSL encryption, select SSL-encrypted and upload the CA Certificate, Client Certificate, and Private Key of Client Certificate as needed. Then, enter the Private Key Password of Client Certificate.

    Note

    • If you select SSL-encrypted for your self-managed PostgreSQL database, you must upload a CA Certificate.

    • If you use a client certificate, you must upload both the Client Certificate and the Private Key of Client Certificate, and enter the Private Key Password of Client Certificate.

    • For information about how to enable SSL encryption for an RDS PostgreSQL instance, see Configure SSL encryption.

    Destination Database

    Select Existing Connection

    • Select the registered database instance with DTS from the drop-down list. The database information below is automatically configured.

      Note

      In the DMS console, this configuration item is Select a DMS database instance.

    • If you have not registered the database instance or do not need to use a registered instance, manually configure the database information below.

    Database Type

    Select PolarDB (Compatible with Oracle).

    Connection Type

    Select Express Connect, VPN Gateway, or Smart Access Gateway.

    Instance Region

    Select the region where the destination PolarDB for PostgreSQL (Compatible with Oracle) cluster resides.

    Connected VPC

    Select the VPC that is connected to the PolarDB for PostgreSQL (Compatible with Oracle) cluster.

    Domain Name or IP Address

    Enter the endpoint of the primary node in the destination PolarDB for PostgreSQL (Compatible with Oracle) cluster.

    Note

    You can run the ping command on your computer to get the IP address for the direct connection endpoint of the destination PolarDB for PostgreSQL (Compatible with Oracle) cluster.

    Port

    Enter the port number used by the destination database. The default value is 1521.

    Database Name

    Enter the name of the destination database that contains the objects to be synchronized in the PolarDB for PostgreSQL (Compatible with Oracle) instance.

    Database Account

    Enter the database account for the destination PolarDB for PostgreSQL (Compatible with Oracle) instance. For information about the required permissions, see Database account permissions.

    Database Password

    Enter the password for the specified database account.

  4. After completing the configuration, click Test Connectivity and Proceed at the bottom of the page.

    Note

    • Ensure that you add the CIDR blocks of the DTS servers (either automatically or manually) to the security settings of both the source and destination databases to allow access. For more information, see Add the IP address whitelist of DTS servers.

    • If the source or destination is a self-managed database (i.e., the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

  5. Configure the task objects.

    1. On the Configure Objects page, specify the objects to synchronize.

      Parameter

      Description

      Synchronization Types

      DTS always selects Incremental Data Synchronization. By default, you must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS initializes the destination cluster with the full data of the selected source objects, which serves as the baseline for subsequent incremental synchronization.

      Processing Mode of Conflicting Tables

      • Precheck and Report Errors: Checks for tables with the same names in the destination database. If any tables with the same names are found, an error is reported during the precheck and the data synchronization task does not start. Otherwise, the precheck is successful.

        Note

        If you cannot delete or rename the table with the same name in the destination database, you can map it to a different name in the destination. For more information, see Database Table Column Name Mapping.

      • Ignore Errors and Proceed: Skips the check for tables with the same name in the destination database.

        Warning

        Selecting Ignore Errors and Proceed may cause data inconsistency and put your business at risk. For example:

        • If the table schemas are consistent and a record in the destination database has the same primary key or unique key value as a record in the source database:

          • During full data synchronization, DTS retains the destination record and skips the source record.

          • During incremental synchronization, DTS overwrites the destination record with the source record.

        • If the table schemas are inconsistent, data initialization may fail. This can result in only partial data synchronization or a complete synchronization failure. Use with caution.

      Source Objects

      In the Source Objects box, click the objects, and then click 向右 to move them to the Selected Objects box.

      Note

      • You can select objects to synchronize at the schema or table level. If you select objects at the table level, other objects such as views, triggers, and stored procedures are not synchronized.

      • If the tables to be synchronized contain columns of the SERIAL data type and you select Schema Synchronization for Synchronization Types, we recommend that you also select Sequence or synchronize the entire schema.

      Selected Objects

      • To rename a single object in the destination instance, right-click the object in the Selected Objects box. For more information, see Map a single object name.

      • To rename multiple objects in bulk, click Batch Edit in the upper-right corner of the Selected Objects box. For more information, see Map multiple object names in bulk.

      Note

      • To select the SQL operations to synchronize for a specific database or table, right-click the object in the Selected Objects box and select the desired operations in the dialog box that appears.

      • To filter data by using a WHERE clause, right-click the table in the Selected Objects box and specify the filter condition in the dialog box that appears. For more information, see Configure filter conditions.

    2. Click Next: Advanced Settings.

      Parameter

      Description

      Dedicated Cluster for Task Scheduling

      By default, DTS uses a shared cluster for tasks, so you do not need to make a selection. For greater task stability, you can purchase a dedicated cluster to run the DTS synchronization task. For more information, see What is a DTS dedicated cluster?.

      Retry Time for Failed Connections

      If the connection to the source or destination database fails after the synchronization task starts, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1,440 minutes. We recommend a duration of 30 minutes or more. If the connection is restored within this period, the task resumes automatically. Otherwise, the task fails.

      Note

      • If multiple DTS instances (e.g., Instance A and B) share a source or destination, DTS uses the shortest configured retry duration (e.g., 30 minutes for A, 60 for B, so 30 minutes is used) for all instances.

      • DTS charges for task runtime during connection retries. Set a custom duration based on your business needs, or release the DTS instance promptly after you release the source/destination instances.

      Retry Time for Other Issues

      If a non-connection issue (e.g., a DDL or DML execution error) occurs, DTS reports an error and immediately retries the operation. The default retry duration is 10 minutes. You can also customize the retry time to a value from 1 to 1,440 minutes. We recommend a duration of 10 minutes or more. If the related operations succeed within the set retry time, the synchronization task automatically resumes. Otherwise, the task fails.

      Important

      The value of Retry Time for Other Issues must be less than that of Retry Time for Failed Connections.

      Enable Throttling for Full Data Synchronization

      During full data synchronization, DTS consumes read and write resources from the source and destination databases, which can increase their load. To mitigate pressure on the destination database, you can limit the migration rate by setting Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s).

      Note

      Enable Throttling for Incremental Data Synchronization

      You can also limit the incremental synchronization rate to reduce pressure on the destination database by setting RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s).

      Environment Tag

      You can select an environment tag to identify the instance. This parameter is optional. You can leave it unspecified for this example.

      Configure ETL

      Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values:

      Monitoring and Alerting

      Choose whether to set up alerts. If the synchronization fails or the latency exceeds the specified threshold, DTS sends a notification to the alert contacts.

    3. Click Data Verification to configure a data verification task.

      To use the data verification feature, see Configure data verification.

  6. Save the task and perform a precheck.

    • To view the parameters for configuring this instance via an API operation, hover over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the tooltip.

    • If you have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.

    Note

    • Before a synchronization task starts, DTS performs a precheck. You can start the task only if the precheck passes.

    • If the precheck fails, click View Details next to the failed item, fix the issue as prompted, and then rerun the precheck.

    • If the precheck generates warnings:

      • For non-ignorable warning, click View Details next to the item, fix the issue as prompted, and run the precheck again.

      • For ignorable warnings, you can bypass them by clicking Confirm Alert Details, then Ignore, and then OK. Finally, click Precheck Again to skip the warning and run the precheck again. Ignoring precheck warnings may lead to data inconsistencies and other business risks. Proceed with caution.

  7. Purchase the instance.

    1. When the Success Rate reaches 100%, click Next: Purchase Instance.

    2. On the Purchase page, select the billing method and link specifications for the data synchronization instance. For more information, see the following table.

      Category

      Parameter

      Description

      New Instance Class

      Billing Method

      • Subscription: You pay upfront for a specific duration. This is cost-effective for long-term, continuous tasks.

      • Pay-as-you-go: You are billed hourly for actual usage. This is ideal for short-term or test tasks, as you can release the instance at any time to save costs.

      Resource Group Settings

      The resource group to which the instance belongs. The default is default resource group. For more information, see What is Resource Management?.

      Instance Class

      DTS offers synchronization specifications at different performance levels that affect the synchronization rate. Select a specification based on your business requirements. For more information, see Data synchronization link specifications.

      Subscription Duration

      In subscription mode, select the duration and quantity of the instance. Monthly options range from 1 to 9 months. Yearly options include 1, 2, 3, or 5 years.

      Note

      This option appears only when the billing method is Subscription.

    3. Read and select the checkbox for Data Transmission Service (Pay-as-you-go) Service Terms.

    4. Click Buy and Start, and then click OK in the OK dialog box.

      You can monitor the task progress on the data synchronization page.

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