Migrate ApsaraDB RDS for MariaDB to ApsaraDB RDS for PostgreSQL - Data Transmission Service

Prerequisites

You have created a destination ApsaraDB RDS for PostgreSQL instance with more storage capacity than the space used by the source ApsaraDB RDS for MariaDB instance. 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 migrated data. For more information, see Create an account and a database.

Limitations

Note

DTS migrates foreign keys during schema migration.
During full and incremental data migration, DTS temporarily disables constraint checks and foreign key cascades at the session level. Cascade updates or deletes on the source database while the task runs may cause data inconsistency.

Type	Description
Source database limitations	The server hosting the source database must have sufficient outbound bandwidth. Otherwise, data migration speed will be reduced. Tables to be migrated must have a primary key or a unique constraint, and all fields in the key or constraint must be unique. Otherwise, the destination database may contain duplicate data. A single data migration task supports up to 1,000 tables when you edit objects at the table level, such as mapping column names. Exceeding this limit causes an error when you submit the task. To migrate more tables, split them into multiple tasks or migrate the entire database. If you perform incremental data migration, the following binlog requirements apply: The binlog feature must be enabled, and the binlog_format and binlog_row_image parameters must be set to row and full, respectively. Otherwise, the precheck fails and the data migration task cannot start. For incremental data migration, the source database must retain its local binlog for more than 24 hours. For tasks that include both full and incremental data migration, DTS requires a binlog retention period of at least 7 days. You can reduce the retention period to more than 24 hours after full data migration is complete. If the task fails due to inaccessible binlog, data inconsistency or loss may occur. The DTS SLA does not cover issues caused by insufficient binlog retention. During the schema migration and full migration phases, do not perform DDL operations that change the database or table schema. Otherwise, the data migration task will fail. Note During the full migration phase, DTS queries the source database. This creates a metadata lock, which may block DDL operations on the source database. If you perform only a full data migration, do not write new data to the source database. Otherwise, data inconsistency will occur between the source and destination databases. To maintain real-time data consistency, select schema migration, full data migration, and incremental data migration. If the data to be migrated contains invisible columns, data loss may occur because DTS cannot retrieve data from these columns.
Other limitations	Do not use tools like pt-online-schema-change to perform online DDL operations on migration objects. Otherwise, the migration will fail. For columns of the FLOAT or DOUBLE data type, DTS reads their values by using `ROUND(COLUMN,PRECISION)`. If the precision is not explicitly defined, DTS uses a default migration precision of 38 digits for FLOAT and 308 digits for DOUBLE. Verify that the migration precision meets your business requirements. Evaluate the performance of the source and destination databases before migration. We recommend migrating data during off-peak hours because full data migration consumes read and write resources and can increase the database server load. During full data migration, concurrent INSERT operations cause table fragmentation in the destination database, resulting in higher storage usage than in the source instance. DTS attempts to resume failed migration tasks within seven days. Before you switch your workloads to the destination instance, terminate or release the DTS instance, or use the `REVOKE` command to revoke write permissions of the DTS account on the destination instance. This prevents automatic task resumption, which could cause source data to overwrite destination data. This limit applies to full or incremental data migration tasks where the tables to be migrated from the source database contain foreign keys, triggers, or event triggers. DTS temporarily sets the `session_replication_role` parameter to `replica` at the session level during the migration. If the destination database account does not have the required permissions, you must manually set the parameter to `replica` in the destination database. During this period (while `session_replication_role` is set to `replica`), cascade update or delete operations in the source database may cause data inconsistency. After the migration task is released, you can set the 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.

Billing

Migration type	Link configuration fee	Internet traffic fee
Schema migration and full data migration	Free of charge.	Migrating data out of Alibaba Cloud over the internet incurs an internet traffic fee. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Schema migration

DTS migrates the schemas of the selected objects from the source to the destination database.
Full data migration

DTS migrates all existing data in the selected objects from the source to the destination database.
Incremental data migration

After full data migration is complete, DTS migrates ongoing data changes from the source to the destination database, minimizing application downtime.

Supported SQL operations for incremental migration

Operation type	SQL statement
DML	INSERT, UPDATE, DELETE

Required permissions for database accounts

Database	Schema migration	Full data migration	Incremental data migration
ApsaraDB RDS for MariaDB instance	SELECT	SELECT	REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT
ApsaraDB RDS for PostgreSQL	CREATE and USAGE on migration objects	Owner permissions on the schema	Owner permissions on the schema

To create accounts and grant permissions:

For an ApsaraDB RDS for MariaDB instance, see Create an account and Modify or reset account permissions.
For an ApsaraDB RDS for PostgreSQL instance, see Create an account and Authorize the service account.

Procedure

Navigate to the migration task list page for the destination region using one of the following methods.
From the DTS console
1. Log on to the Data Transmission Service (DTS) console.
2. In the navigation pane on the left, click Data Migration.
3. In the upper-left corner of the page, select the region where the migration instance is located.
From the DMS console

Note
The actual operations may vary based 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 Data Management (DMS) console.
2. In the top menu bar, choose Data + AI > Data Transmission (DTS) > Data Migration.
3. To the right of Data Migration Tasks, select the region where the migration instance is located.
Click Create Task to navigate to the task configuration page.
Optional: In the upper-right corner of the page, click New Configuration Page.
Note
- If you are already on the new configuration page (the button in the upper-right corner is Back to Previous Version), you can skip this step.
- The parameters on the new and old configuration pages are different. We recommend that you use the new configuration page.

Configure the source and destination databases.

Section	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. Specify a descriptive name for easier identification. The name does not need to be unique.
Source Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select MariaDB.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the source ApsaraDB RDS for MariaDB instance is located.
	Replicate Data Across Alibaba Cloud Accounts	In this example, a database instance under the current Alibaba Cloud account is used. Select No.
	Instance ID	Select the instance ID of the source ApsaraDB RDS for MariaDB instance.
	Database Account	Enter the database account for the source ApsaraDB RDS for MariaDB instance. For permission requirements, see Required permissions for database accounts.
	Database Password	Enter the password for the database account.
	Connection Method	The default connection method for an ApsaraDB RDS for MariaDB instance is Non-encrypted.
Destination Database	Select Existing Connection	To use a database instance that has been added to the system (created or saved), select the desired database instance from the drop-down list. The database information below will be automatically configured. Note In the DMS console, this parameter is named Select a DMS database instance.. If you have not registered the database instance with the system, or do not need to use a registered instance, manually configure the database information below.
	Database Type	Select PostgreSQL.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination ApsaraDB RDS for PostgreSQL instance is located.
	Instance ID	Select the instance ID of the destination ApsaraDB RDS for PostgreSQL instance.
	Database Name	Enter the name of the destination database that will receive the migrated objects.
	Database Account	Enter the database account for the destination ApsaraDB RDS for PostgreSQL instance.
	Database Password	Enter the password for the database account.
	Encryption	Specifies whether to encrypt the connection to the source database. You can configure this parameter based on your business requirements. In this example, Non-encrypted is selected. If you want to establish an SSL-encrypted connection to the source database, perform the following steps: Select SSL-encrypted, upload CA Certificate, Client Certificate, and Private Key of Client Certificate as needed, and then specify Private Key Password of Client Certificate. Note If you set Encryption to SSL-encrypted for a self-managed PostgreSQL database, you must upload CA Certificate. If you want to use the client certificate, you must upload Client Certificate and Private Key of Client Certificate and specify Private Key Password of Client Certificate. For information about how to configure SSL encryption for an ApsaraDB RDS for PostgreSQL instance, see SSL encryption.

After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.
Note
- Ensure that the IP address segment of the DTS service is automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add DTS server IP addresses to a whitelist.
- If the source or destination database is a self-managed database (the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box that appears.

Configure the task objects.

On the Configure Objects page, configure the objects that you want to migrate.

Parameter	Description
Migration Types	If you only need to perform a full migration, select both Schema Migration and Full Data Migration. To perform a migration with no downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Schema Migration, you must ensure that a database and tables to receive the data exist in the destination database. You can also use the object name mapping feature in the Selected Objects box as needed. If you do not select Incremental Data Migration, do not write new data to the source instance during data migration to ensure data consistency.
Processing Mode of Conflicting Tables	Precheck and Report Errors: Checks whether tables with the same names exist in the destination database. If no tables with the same names exist, the precheck is passed. If tables with the same names exist, an error is reported during the precheck, and the data migration task does not start. Note If a table in the destination database has the same name but cannot be easily deleted or renamed, you can change the name of the table in the destination database. For more information, see Object name mapping. Ignore Errors and Proceed: Skips the check for tables with the same names. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and business risks. For example: If the table schemas are consistent and a record in the destination database has the same primary key value as a record in the source database: During full migration, DTS keeps the record in the destination database. The record from the source database is not migrated. During incremental migration, DTS does not keep the record in the destination database. The record from the source database overwrites the record in the destination database. If the table schemas are inconsistent, only some columns of data may be migrated, or the migration may fail. Proceed with caution.
Source Objects	In the Source Objects box, click the objects to migrate, and then click to move them to the Selected Objects box. Note You can select objects at the database, table, or column level.
Selected Objects	To change the name of a single migration object in the target instance, right-click the object in the Selected Objects box. For more information, see Map individual schema, table, and column names. To change the names of multiple migration objects in the target instance, click Selected Objects in the upper-right corner of the Batch Edit box. For more information, see Map multiple schema, table, and column names. Note If you use the object name mapping feature, other objects that depend on the renamed object may fail to migrate. To specify a WHERE clause to filter data, right-click the table in the Selected Objects panel and set the filter condition in the dialog box that appears. For more information, see Set filter conditions. To select the SQL operations to migrate at the database or table level, right-click the object in the Selected Objects panel and select the desired SQL operations in the dialog box that appears.

Click Next: Advanced Settings to configure advanced parameters.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS schedules tasks on a shared cluster. You do not need to select one. If you want more stable tasks, you can purchase a dedicated cluster to run DTS migration tasks.
Retry Time for Failed Connections	After the migration task starts, if the connection to the source or destination database fails, 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 1440 minutes. We recommend that you set the duration to more than 30 minutes. If DTS reconnects to the source and destination databases within the specified duration, the migration task automatically resumes. Otherwise, the task fails. Note For multiple DTS instances that share the same source or destination, the network retry time is determined by the setting of the last created task. Because you are charged for the task during the connection retry period, we recommend that you customize the retry time based on your business needs, or release the DTS instance as soon as possible after the source and destination database instances are released.
Retry Time for Other Issues	After the migration task starts, if a non-connectivity issue, such as a DDL or DML execution exception, occurs in the source or destination database, DTS reports an error and immediately begins to retry the operation. The default retry duration is 10 minutes. You can customize the retry time to a value from 1 to 1440 minutes. We recommend that you set the duration to more than 10 minutes. If the related operations succeed within the specified retry duration, the migration task automatically resumes. Otherwise, the task fails. Important The value of Retry Time for Other Issues must be less than the value of Retry Time for Failed Connections.
Enable Throttling for Full Data Migration	During full migration, DTS consumes read and write resources on the source and destination databases, which may increase the database load. If required, you can enable throttling for the full migration task. You can set Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) to reduce the load on the destination database. Note This configuration item is available only if you select Full Data Migration for Migration Types. You can also adjust the full migration speed after the migration instance is running.
Enable Throttling for Incremental Data Migration	If required, you can also choose to set speed limits for the incremental migration task. You can set RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) to reduce the load on the destination database. Note This configuration item is available only if you select Incremental Data Migration for Migration Types. You can also adjust the incremental migration speed after the migration instance is running.
Environment Tag	You can select an environment tag to identify the instance. No selection is required for this example.
Configure ETL	Based on your business needs, select whether to configure the ETL feature to process data. Yes: Configures the ETL feature. You must also enter data processing statements in the text box. No: Does not configure the ETL feature.
Monitoring and Alerting	Select whether to set alerts and receive alert notifications based on your business needs. No: Does not set an alert. Yes: Configure alerts by setting an alert threshold and an alert notifications. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.

Save the task and run a precheck.
- To view the parameters for configuring this instance when you call the API operation, move the pointer over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the bubble that appears.
- If you do not need to view or have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note
- Before the migration task starts, DTS performs a precheck. The task starts only after it passes the precheck.
- If the precheck fails, click View Details next to the failed check item, fix the issue based on the prompt, and then run the precheck again.
- If a warning is reported during the precheck:
  
  For check items that cannot be ignored, click View Details next to the failed item, fix the issue based on the prompt, and then run the precheck again.
  
  For check items that can be ignored, you can click Confirm Alert Details, Ignore, OK, and Precheck Again to skip the alert item and run the precheck again. If you choose to ignore a warning, it may cause issues such as data inconsistency and pose risks to your business.

Purchase the migration instance.

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

On the Purchase page, select the link specification for the data migration instance. For more information, see the following table.

Category	Parameter	Description
New Instance Class	Resource Group Settings	Select the resource group to which the instance belongs. The default value is default resource group. For more information, see What is Resource Management?
New Instance Class	Instance Class	DTS provides migration specifications with different performance levels. The link specification affects the migration speed. You can select a specification based on your business scenario. For more information, see Data migration link specifications.

After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start. In the OK dialog box that appears, click OK.

You can view the progress of the migration task on the Data Migration Tasks list page.
Note
- If the migration task does not include incremental migration, it stops automatically after the full migration is complete. After the task stops, its Status changes to Completed.
- If the migration task includes incremental migration, it does not stop automatically. The incremental migration task continues to run. While the incremental migration task is running, the Status of the task is Running.