Migrate data from PolarDB-X 1.0 to the cloud-native data warehouse AnalyticDB for PostgreSQL-Data Transmission Service(DTS)-阿里云帮助中心

Prerequisites

The storage type for PolarDB-X 1.0 must be ApsaraDB RDS for MySQL. PolarDB for MySQL is not currently supported.
You have created a destination AnalyticDB for PostgreSQL instance. The destination instance must have more storage capacity than the space used by the source PolarDB-X 1.0 instance. For more information, see Create an instance.
You have created a database in the destination AnalyticDB for PostgreSQL instance to receive the migrated data. For more information, see CREATE DATABASE.

Usage notes

Type

Description

Source database limitations

Bandwidth requirements: The server that hosts the source database must have sufficient outbound bandwidth. Insufficient bandwidth will slow down the data migration.
Tables to be migrated must have a PRIMARY KEY or a UNIQUE constraint, and the fields in the key or constraint must be unique. Otherwise, this may cause duplicate data in the destination database.
If you migrate objects at the table level and need to edit them, for example, by mapping column names, a single data migration task supports a maximum of 1,000 tables. If you exceed this limit, the task submission will fail. In this case, split the tables into multiple data migration tasks or configure a task to migrate the entire database.
For incremental migration, you must ensure that the binlog_row_image parameter of the RDS MySQL instance attached to PolarDB-X 1.0 is set to full. Otherwise, the precheck fails and the data migration task cannot start.
Note
For an incremental migration task, DTS requires the source database to retain its local binlog for more than 24 hours. If your task includes both full and incremental migration, you must retain the binlog for at least 7 days. You can change the retention period to more than 24 hours after the full migration is complete. If the retention period is too short, the migration task might fail because DTS cannot obtain the required binlog files. In extreme cases, this can lead to data inconsistency or data loss. The DTS SLA does not cover problems caused by an insufficient binlog retention period.

The storage type for PolarDB-X 1.0 must be RDS MySQL. PolarDB for MySQL is not supported.
Operational restrictions on the source database:
- If you need to switch the network type of the PolarDB-X 1.0 instance during migration, update the network connection settings of the migration link after the switch is complete.
- During the migration, do not scale the source instance up or down, migrate hot-spot tables, change shard keys, or execute DDL statements. Otherwise, the migration task may fail or data inconsistency may occur.
- If the partition key is changed in the source database and the primary key in the target table does not include the source partition key, data loss may occur in the target database.
  - Reason: A PolarDB-X 1.0 instance has multiple RDS for MySQL instances attached to it. DTS creates a separate migration link for each RDS for MySQL instance. A change to a partition key causes data to be deleted from one RDS for MySQL instance and inserted into another. Because the links execute independently, the execution order of the DELETE and INSERT operations is not guaranteed. If the primary key of the target database does not include the partition key, a DELETE operation that executes later may accidentally delete the newly inserted data.
  - Recommendation: To prevent data loss caused by out-of-order operations, ensure that the primary key of the target table includes the partition key column from the source database.
The source PolarDB-X 1.0 instance must be version 5.2 or later. To view the version of an instance, see Overview of instance versions.
Do not change the type of a broadcast table in the source PolarDB-X 1.0 instance while a DTS migration task is running (for example, from a broadcast table to a single table or a sharded table). If you need to change the table type, stop the migration task. After the change is complete, reconfigure the migration task.

Other limitations

DTS does not support append-optimized (AO) tables as target tables.
DTS does not support migrating data of the GEOMETRY, CURVE, SURFACE, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, and GEOMETRYCOLLECTION types.
DTS does not support migrating INDEX, PARTITION, VIEW, PROCEDURE, FUNCTION, TRIGGER, and FK objects.
If you use column mapping for a partial table migration or if the source and target table schemas are inconsistent, data from columns that exist in the source but not the target will be lost.
DTS does not support read-only instances of PolarDB-X 1.0 compute resources.
DTS supports only horizontal sharding for PolarDB-X 1.0 storage resources, not vertical sharding.
Because a migration task for PolarDB-X 1.0 is distributed, each attached RDS MySQL instance maps to one migration subtask. You can view the status of subtasks in Task Topology.
DTS relies on the continuity of XA transactions in the source PolarDB-X 1.0 instance to ensure data consistency for incremental migration tasks. If the continuity of XA transactions is broken, for example, during a disaster recovery scenario for the incremental data capture module, uncommitted XA transactions may be lost.
If a table to be migrated has a primary key, the primary key column in the destination table must be the same as that in the source table. If a table to be migrated does not have a primary key, the primary key column in the destination table must be the same as the distribution key.
The unique key of the destination table, including the primary key column, must contain all columns of the distribution key.
Before you start data migration, evaluate the performance of both the source and target databases. Run data migration during off-peak hours. Full data initialization consumes some read and write resources on the source and target databases, which can increase the database load.
Full data initialization runs concurrent INSERT operations, which can fragment tables in the target database. As a result, after full data initialization is complete, tablespaces on the target instance are larger than those on the source instance.
During DTS migration, do not write data to the target database. Only DTS is permitted to write to the target to avoid data inconsistencies.
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	Public traffic fee
Schema migration and full data migration	Free of charge.	No charges are incurred in this tutorial.
Incremental data migration	Charged. For more information, see Billing overview.	No charges are incurred in this tutorial.

Supported SQL for incremental migration

Operation type	SQL statement
DML	INSERT, UPDATE, DELETE Note The system automatically converts an UPDATE statement to a REPLACE INTO statement when writing to the destination AnalyticDB for PostgreSQL instance. If an UPDATE statement modifies a primary key, the system converts it into DELETE and INSERT statements.

Permissions required for database accounts

Database	Schema Migration	Full Data Migration	Incremental Data Migration
Source PolarDB-X 1.0 instance	SELECT	SELECT	Read and write permissions on the migration objects.
Destination AnalyticDB for PostgreSQL instance	Read and write permissions on the destination database. Note You can also use the initial account or an account that has the RDS_SUPERUSER permission.

For more information about how to create a database account and grant permissions, see the following topics:

For a PolarDB-X 1.0 instance, see Manage accounts.
For an AnalyticDB for PostgreSQL instance, see Create and manage users and Manage user permissions.

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.

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	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 PolarDB-X 1.0.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the source PolarDB-X 1.0 instance resides.
	Replicate Data Across Alibaba Cloud Accounts	This example migrates data within the same Alibaba Cloud account. Select No.
	Instance ID	Select the ID of the source PolarDB-X 1.0 instance.
	Database Account	Enter the database account of the source PolarDB-X 1.0 instance. For information about the required permissions, see Permissions required for database accounts.
	Database Password	Enter the password for the specified database account.
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 AnalyticDB for PostgreSQL.
	Access Method	Select Alibaba Cloud Instance.
	Instance Region	Select the region where the destination AnalyticDB for PostgreSQL instance resides.
	Instance ID	Select the ID of the destination AnalyticDB for PostgreSQL instance.
	Database Name	Enter the name of the database in the destination AnalyticDB for PostgreSQL instance that will receive the migrated objects.
	Database Account	Enter the database account of the destination AnalyticDB for PostgreSQL instance. For information about the required permissions, see Permissions required for database accounts.
	Database Password	Enter the password for the specified database account.

After you complete the configuration, click Test Connectivity and Proceed at the bottom of the page.

Note
Ensure that the DTS service IP address segments are 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.

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.
Storage Engine Type	Select a storage engine for the destination tables based on your business requirements. The default value is Beam. Note This parameter is available only if the destination AnalyticDB for PostgreSQL instance has a kernel version of v7.0.6.6 or later and you selected Migration Types for the Schema Migration parameter.
Capitalization of Object Names in Destination Instance	You can configure the case sensitivity policy for the names of migrated objects, such as databases, tables, and columns, in the destination instance. By default, DTS default policy is selected. You can also choose to keep the case sensitivity consistent with the default policy of the source or destination database. For more information, see Case sensitivity of object names in the destination database.
Source Objects	In the Source Objects box, click the objects to migrate, and then click to move them to the Selected Objects box. Note Select objects to migrate at the table level. If you select an entire database, any changes to add or delete tables in that database will not be migrated to the destination.
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 might fail to be migrated. To filter data by using a WHERE clause, right-click a table in the Selected Objects panel and specify the filter condition in the dialog box that appears. For more information, see Set filter conditions.

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.
	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 contact. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.
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 based on your business requirements. No tag is selected in this tutorial.
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 contact. If a migration fails or the latency exceeds the threshold, the system sends an alert notification.

Optional: Click Next: Configure Database and Table Fields to set the Type, Primary Key Column, and Distribution Key for the tables to be migrated to the destination AnalyticDB for PostgreSQL instance.
Note
- This step is available only if you select Schema Migration for Migration Types when you configure migration objects. You can select All for Definition Status and then make modifications.
- You can select multiple columns for Primary Key Column to form a composite primary key. You must also select one or more columns from the Primary Key Column as the Distribution Key. For more information, see Manage data tables and Define table distribution.

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 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.