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Migrate self-managed PostgreSQL to RDS PostgreSQL

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This topic describes how to use Data Transmission Service (DTS) to synchronize data from a self-managed PostgreSQL database to ApsaraDB RDS for PostgreSQL.

Prerequisites

  • You have created a source self-managed PostgreSQL database and a destination RDS PostgreSQL instance. For more information about how to create an RDS PostgreSQL instance, see Create an RDS PostgreSQL instance.

    Note

    • For the supported versions of the source and destination databases, see synchronization solution overview.

    • We recommend using a destination database version that is the same as or later than the source database's version. Synchronizing data to an earlier version may cause compatibility issues.

  • The storage space of the destination RDS PostgreSQL instance must be larger than the storage space used by the source self-managed PostgreSQL database.

Notes

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.

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

  • 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.

  • DTS does not synchronize temporary tables, internal triggers, or some functions (C language functions and internal functions for PROCEDURE and FUNCTION) from the source database. DTS synchronizes some custom data types (COMPOSITE, ENUM, or RANGE) and the following constraints: primary key, foreign key, unique, and CHECK.

  • 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

  • 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.

  • 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.

  • 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.

  • For a task that performs full or incremental synchronization, if the tables to be synchronized in the source database contain foreign keys, triggers, or event triggers, and the destination database account is a privileged account or has superuser permissions, DTS temporarily sets the session_replication_role parameter to replica at the session level during synchronization. If the destination database account does not have these permissions, you must manually set the session_replication_role parameter to replica in the destination database. During this period (when session_replication_role is set to replica), if cascade update or delete operations occur in the source database, data inconsistency may occur. After the DTS task is released, you can change the value of the session_replication_role parameter back to origin.

  • 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.

Pricing

Synchronization type

Fees

Schema synchronization and full synchronization

Free.

Incremental synchronization

Fees apply. See billing overview.

Supported 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 an introduction to each synchronization topology, see data synchronization topologies.

Supported objects for synchronization

  • SCHEMA, TABLE.

    Note

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

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

Supported SQL operations for synchronization

Operation type

SQL operation

DML

INSERT, UPDATE, DELETE

DDL

  • DDL synchronization is supported only for data synchronization tasks created after October 1, 2020 (Beijing time)October 1, 2020 (Singapore time).

    Important

  • The synchronization task supports the following DDL operations, provided the source database account is a high-privilege account and the self-managed PostgreSQL database has minor version 20210228 or later.

    • CREATE TABLE, 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 (requires the source database to be PostgreSQL 11 or later)

    • CREATE INDEX ON TABLE

    Important

    • DDL statements that include additional information, such as CASCADE or RESTRICT, are not supported.

    • DDL statements in a session that uses the SET session_replication_role = replica command are not synchronized.

    • DDL statements executed by calling a FUNCTION are not supported.

    • If a commit contains both DML and DDL operations, the DDL operations are not synchronized.

    • If a commit contains DDL operations on objects that are not being synchronized, those operations are not synchronized.

    • DDL statements executed directly within a plugin through the SPI (Server Programming Interface) are not supported.

Required permissions for database accounts

Database

Required permissions

Account creation and authorization

Self-managed PostgreSQL

superuser permission

Use the CREATE USER and GRANT statements.

RDS PostgreSQL

A high-privilege account that must also be the owner (authorized account) of the selected database.

Create Account.

Preparations

Note

The following steps apply to Linux systems.

Perform the following preparations for self-managed PostgreSQL (all versions).

  1. Log on to the server where the self-managed PostgreSQL database is deployed.

  2. Run the following command to check the number of replication slots in use.

    select count(1) from pg_replication_slots;

  3. Modify the postgresql.conf file to set wal_level to logical. Also ensure that the values of the max_wal_senders and max_replication_slots parameters are greater than the sum of the number of replication slots currently in use and the number of DTS instances you plan to create with this self-managed PostgreSQL database as the source.

    # - 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-managed PostgreSQL database for the changes to take effect.

  4. Add the DTS IP address to the pg_hba.conf file of the self-managed PostgreSQL database. Add only the DTS IP address range corresponding to the region of the destination database. For more information, see Add DTS server IP addresses to the whitelist.

    Note

    • After modifying the configuration file, run the command SELECT pg_reload_conf(); or restart the self-managed PostgreSQL database for the changes to take effect.

    • For more information about this configuration file, see pg_hba.conf file. If you have already configured the trust address as 0.0.0.0/0 (as shown in the following code), skip this step.

    # "local" is for Unix domain socket connections only
local   all             all                                     trust
# IPv4 local connections:
host    all             all             0.0.0.0/0               md5
# IPv6 local connections:
host    all             all             ::1/128                 trust
# Allow replication connections from localhost, by a user with the
# replication privilege.
local   replication     postgres                                trust
host    replication     postgres        0.0.0.0/0               md5

  5. Create the corresponding database and schema in the destination RDS PostgreSQL instance based on the database and schema information of the objects to be synchronized (schema names must match). For more information, see Create a database and Schema management.

If your self-managed PostgreSQL version is between 9.4.8 and 10.0, you must also perform the following preparations.

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

    1. Log on to the server where the self-managed PostgreSQL database is deployed.

    2. Download the source code for your self-managed PostgreSQL version from the PostgreSQL official website.

    3. Run the commands sudo ./configure, sudo make, and sudo make install to configure, compile, and install the source code.

      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 running 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., adjust the command to sudo ./configure --without-readline.

      • If you choose another method to install PostgreSQL, compile ali_decoding in a test environment with the same operating system and GCC versions.

  2. Download and compile the ali_decoding plug-in provided by DTS.

    1. Download ali_decoding.

    2. Copy the entire ali_decoding directory to the contrib directory of PostgreSQL (after compilation and installation).

      total 1068
-rw-r--r--  1 1107 1107    384 Sep 27  2016 aclocal.m4
drwxrwxrwx  2 1107 1107   4096 Sep 27  2016 config
-rw-r--r--  1 root root 374806 Sep  7 10:10 config.log
-rwxr-xr-x  1 root root  39032 Sep  7 10:10 config.status
-rwxr-xr-x  1 1107 1107 471157 Sep 27  2016 configure
-rw-r--r--  1 1107 1107  75195 Sep 27  2016 configure.in
drwxrwxrwx 56 1107 1107   4096 Sep  7 10:28 contrib
-rw-r--r--  1 1107 1107   1192 Sep 27  2016 COPYRIGHT
drwxrwxrwx  3 1107 1107   4096 Sep 27  2016 doc
-rw-r--r--  1 root root   3638 Sep  7 10:10 GNUmakefile
-rw-r--r--  1 1107 1107   3638 Sep 27  2016 GNUmakefile.in
-rw-r--r--  1 1107 1107    283 Sep 27  2016 HISTORY
-rw-r--r--  1 1107 1107  75065 Sep 27  2016 INSTALL
-rw-r--r--  1 1107 1107   1489 Sep 27  2016 Makefile
-rw-r--r--  1 1107 1107   1209 Sep 27  2016 README
drwxrwxrwx 16 1107 1107   4096 Sep  7 10:10 src

    3. Go 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 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. Go to the ali_decoding directory and run the commands sudo make and sudo make install to compile ali_decoding and obtain the files needed for installation.

    5. Copy the following files to the specified locations.

      /usr/bin/install -c -m 755  ali_decoding.so '/usr/local/pgsql/lib/ali_decoding.so'
/usr/bin/install -c -m 644 ./ali_decoding.control '/usr/local/pgsql/share/extension/'
/usr/bin/install -c -m 644 ./ali_decoding--0.0.1.sql ./ali_decoding--unpackaged--0.0.1.sql  '/usr/local/pgsql/share/extension/'
/usr/bin/install -c -m 755  ali_decoding.so '/usr/local/pgsql/lib/'

  3. Create the corresponding database and schema in the destination RDS PostgreSQL instance based on the database and schema information of the objects to be synchronized (schema names must match). For more information, see Create a database and Schema management.

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 DMS console layout and style.

    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.

    Warning

    After you select the source and destination instances, review the Limits at the top of the page. Otherwise, the task may fail or data inconsistency may occur.

    Category

    Configuration

    Description

    None

    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

    Database Type

    Select PostgreSQL.

    Access Method

    Select Cloud Enterprise Network (CEN).

    Instance Region

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

    CEN Instance ID

    Select the CEN instance ID associated with the self-managed PostgreSQL database.

    Connected VPC

    Select the VPC network connected to the self-managed PostgreSQL database.

    Domain Name or IP

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

    Port Number

    Enter the port used by the self-managed PostgreSQL database. The default port is 3433.

    Database Name

    Enter the name of the database in the self-managed PostgreSQL instance that contains the objects to be synchronized.

    Database Account

    Enter the database account for the self-managed PostgreSQL instance. For required permissions, see Required permissions for database accounts.

    Database Password

    Enter the password for the specified database account.

    Encryption

    Select a connection method. In this example, Non-encrypted is selected.

    If you need to connect to the database by using SSL encryption, select SSL-encrypted, and then 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 a self-managed PostgreSQL database, you must upload the CA Certificate.

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

    • For information about the SSL encryption feature for an RDS for PostgreSQL instance, see SSL connection encryption.

    Destination Database

    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 instance ID of the destination RDS PostgreSQL instance.

    Database Name

    Enter the name of the database in the destination RDS PostgreSQL instance that contains the objects to be synchronized.

    Database Account

    Enter the database account for the destination RDS PostgreSQL instance. For required permissions, see Required permissions for database accounts.

    Database Password

    Enter the password for the specified database account.

    Encryption

    Select a connection method. In this example, Non-encrypted is selected.

    If you need to connect to the database by using SSL encryption, select SSL-encrypted, and then 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 a self-managed PostgreSQL database, you must upload the CA Certificate.

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

    • For information about the SSL encryption feature for an RDS for PostgreSQL instance, see SSL connection encryption.

  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.

      Configuration

      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.

      Note

      If you select Schema Synchronization, DTS synchronizes the structure of the tables to be synchronized from the source database (including foreign keys) to the destination database.

      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 Object 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.

      Synchronization Topology

      This scenario involves one-way synchronization. Select One-way Synchronization.

      Capitalization of Object Names in Destination Instance

      Configure the case-sensitivity policy for database, table, and column names in the destination instance. By default, the DTS default policy is selected. You can also choose to use the default policy of the source or destination database. For more information, see Case policy for destination object names.

      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 tables as the synchronization objects, other objects such as views, triggers, and stored procedures are not synchronized to the target database.

      • If a table to be synchronized contains a field of the SERIAL type and Synchronization Types is selected for Schema Synchronization, we recommend also selecting Sequence or 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 SQL operations to synchronize at the database or table level, right-click the object to be synchronized in Selected Objects and select the required SQL operations in the dialog box that appears.

      • To set a WHERE clause to filter data, right-click the table to be synchronized in Selected Objects and set the filter condition in the dialog box that appears. For more information, see Set filter conditions.

      • If you use the object name mapping feature, it may cause synchronization failures for other objects that depend on this object.

    2. Click Next: Advanced Settings.

      Configuration

      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

      Based on your needs, select an environment tag to identify the instance.

      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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