Synchronize ApsaraDB RDS for MariaDB to ApsaraDB RDS for PostgreSQL-Data Transmission Service(DTS)-阿里云帮助中心

Prerequisites

You have created a destination ApsaraDB RDS for PostgreSQL instance with more available storage space than the source instance uses. For more information, see Quickly create an ApsaraDB RDS for PostgreSQL instance.
You have created a database in the destination ApsaraDB RDS for PostgreSQL instance to store the synchronized data. For more information, see Create an account and a 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 limitations	The tables to be synchronized must have primary keys or unique constraints, and all fields in the constraints must be unique. Otherwise, the destination database may contain duplicate data. If you select tables as the synchronization objects and need to edit them, for example, by mapping column names, a single synchronization task supports a maximum of 1,000 tables. If you exceed this limit, the task reports an error upon submission. To avoid this, split the tables into multiple tasks or configure a single task to synchronize the entire database. Binary log: By default, binary logging is enabled for an ApsaraDB RDS for MariaDB instance. You must ensure that the `binlog_row_image` parameter is set to `full`. Otherwise, the precheck reports an error and prevents the data synchronization task from starting. For more information about how to set parameters, see Set instance parameters. The DTS Service Level Agreement (SLA) does not cover issues caused by an insufficient binary log retention period. For incremental data synchronization tasks, DTS requires that the local binary logs of the source database be retained for at least 24 hours. For tasks that include both full and incremental data synchronization, the binary logs must be retained for at least 7 days. You can change the retention period to 24 hours or more after full data synchronization is complete. If DTS cannot obtain the binary logs, the task may fail. In extreme cases, data inconsistency or loss may occur. 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 the data to be synchronized contains invisible columns, data loss may occur because DTS cannot retrieve data from these columns.
Other limitations	To ensure compatibility, we recommend that you use the same database version for the source and destination databases, or synchronize data from an earlier version to a later version. If you synchronize data from a later version to an earlier version, compatibility issues may occur. Before you synchronize data, evaluate the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. Full data synchronization consumes read and write resources on the source and destination databases, increasing their load. After full data synchronization is complete, the table space in the destination instance is larger than that in the source instance. Concurrent INSERT operations during full data synchronization can cause table fragmentation in the destination database. If you synchronize one or more tables instead of an entire database, do not use tools such as pt-online-schema-change to perform online DDL operations on the synchronization objects in the source database. Otherwise, the synchronization task fails. You can use Data Management (DMS) to perform online DDL operations. For more information, see Perform lock-free schema changes. During DTS synchronization, do not write data to the destination database by using external tools. Otherwise, data inconsistency may occur between the source and destination databases. For example, if you use DMS to perform online DDL changes while data is being written to the destination database from another source, data loss may occur in the destination database. The Timestamp data type is supported for time fields. If a time field in the source database has a value of 0, it is automatically converted to null 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.
Special cases	If the source is a self-managed MariaDB database: If a primary/secondary switchover occurs on the source database during synchronization, the task fails. DTS calculates latency by comparing the timestamp of the last synchronized data in the destination database with the current timestamp. If no DML operations are performed on the source database for an extended period, the displayed latency may be inaccurate. If the task shows an excessively large latency, you can perform a DML operation on the source database to update the latency information. Note If you synchronize an entire database, you can also create a heartbeat table. The heartbeat table is updated or written to every second. DTS periodically runs the CREATE DATABASE IF NOT EXISTS `test` command on the source database to advance the binary log position.

Billing

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

Supported synchronization topologies

One-way one-to-one synchronization
One-way one-to-many synchronization
One-way many-to-one synchronization

Supported SQL operations

Operation type	SQL operations
DML	INSERT, UPDATE, DELETE

Database account permissions

Database	Permissions	Actions
ApsaraDB RDS for MariaDB instance	SELECT	Create an account and Modify or reset account permissions
ApsaraDB RDS for PostgreSQL instance	CREATE and USAGE permissions on the objects to be migrated, and owner of the schema	Create an account and Authorize a service account

Procedure

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.
Click Create Task to open the task configuration page.

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 MariaDB.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the source ApsaraDB RDS for MariaDB instance resides.
	Replicate Data Across Alibaba Cloud Accounts	For this example, select No, as the database instance belongs to the current Alibaba Cloud account.
	Instance ID	Select the ID of the source ApsaraDB RDS for MariaDB instance.
	Database Account	Enter the database account for the source ApsaraDB RDS for MariaDB instance.
	Database Password	Enter the password for the specified database account.
	Connection method	Select Non-encrypted.
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 PostgreSQL.
	Connection Type	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination ApsaraDB RDS for PostgreSQL instance resides.
	Instance ID	Select the ID of the destination ApsaraDB RDS for PostgreSQL instance.
	Database Name	Enter the name of the database that contains the synchronization objects in the destination ApsaraDB RDS for PostgreSQL instance.
	Database Account	Enter the database account for the destination ApsaraDB RDS for PostgreSQL instance. The account must be the owner of the schema. For information about how to create an account, see Create an account.
	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.

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.

Configure the task objects.

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

Parameter	Description
Synchronization Types	The synchronization types. By default, Incremental Data Synchronization is selected. You must also select Schema Synchronization and Full Data Synchronization. After the precheck is complete, DTS synchronizes the historical data of the selected objects from the source database to the destination cluster. The historical data is the basis for subsequent incremental synchronization.
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 to move them to the Selected Objects box. Note You can select objects at the database, table, or column level. If you select only tables or columns, DTS does not synchronize other object types (such as views, triggers, and stored procedures).
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.

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 This parameter is available only if Synchronization Types is set to Full Data Synchronization. You can also adjust the rate of full data synchronization when the synchronization instance is running.
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 based on your requirements. In this example, you do not need to select a tag.
Configure ETL	Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: Enables the ETL feature. Enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: Disables the ETL feature.
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. No: No alerts are configured. Yes: Configures alerts. You must also set the alert threshold and alert contact. For more information, see Configure monitoring and alerting during task configuration.

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.

Purchase the instance.

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

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.

Read and select the checkbox for Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start, and then click OK in the OK dialog box.
You can monitor the task progress on the data synchronization page.