Migrate data from PolarDB-X 1.0 to AnalyticDB for PostgreSQL - Data Transmission Service

Prerequisites

The storage class of the source PolarDB-X 1.0 instance must be RDS MySQL. PolarDB for MySQL is not supported.
Create an AnalyticDB for PostgreSQL destination instance. The storage space of the destination instance must be larger than the storage space used by the source PolarDB-X 1.0 instance. For more information, see Create an instance.
Create a database in the destination AnalyticDB for PostgreSQL instance to store the migrated data. For more information, see CREATE DATABASE.

Usage notes

Type

Description

Source database limits

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, the binlog_row_image parameter of the RDS MySQL instance mounted to the PolarDB-X 1.0 instance must be set to full. Otherwise, an error is reported during the precheck and the data migration task cannot start.

Note
For an incremental migration task, DTS requires that the local binary logs of the source database are retained for more than 24 hours. For a task that includes both full migration and incremental migration, DTS requires that the local binary logs of the source database are retained for at least 7 days. You can change the retention period to more than 24 hours after the full migration is complete. Otherwise, the task may fail because DTS cannot obtain the binary logs. In extreme cases, data inconsistency or data loss may occur. Issues caused by a binary log retention period that is shorter than the period required by DTS are not covered by the DTS Service-Level Agreement (SLA).

The storage class of the PolarDB-X 1.0 instance can be RDS MySQL. PolarDB for MySQL is not supported.
Operational limits on the source database:
- To switch the network type of the PolarDB-X 1.0 instance during migration, adjust the network connection information of the migration link after the switch is successful.
- During migration, do not perform operations such as scale-out, scale-in, hot spot table migration, shard key changes, or DDL changes on the source instance. Otherwise, the data migration task may fail or data inconsistency may occur.
- If the partition key is changed in the source database and the primary key of the destination table does not contain the partition key of the source table, data loss may occur in the destination database.
  - Cause: A PolarDB-X 1.0 instance has multiple RDS MySQL instances mounted. DTS creates independent migration links for each RDS MySQL instance. A partition key change causes data to be deleted from one RDS MySQL instance and inserted into another. Because the links are independent, the order of DELETE and INSERT operations may be disrupted. If the primary key of the destination table does not contain the partition key, a later DELETE operation may incorrectly delete the inserted data.
  - Suggestion: Make sure that the primary key of the destination table contains the partition key columns of the source table. This prevents data loss caused by out-of-order operations.
The source PolarDB-X 1.0 instance must be version 5.2 or later.

Other limits

Append-optimized (AO) tables are not supported as destination tables.
Migration of data of the GEOMETRY, CURVE, SURFACE, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, and GEOMETRYCOLLECTION types is not supported.
Migration of INDEX, PARTITION, VIEW, PROCEDURE, FUNCTION, TRIGGER, and FK is not supported.
If you use column mapping for a partial table migration or if the source and destination table schemas are inconsistent, data in the columns that exist in the source table but not in the destination table is lost.
Read-only instances of PolarDB-X 1.0 compute resources are not supported.
Only horizontal splitting (sharding) is supported for PolarDB-X 1.0 storage resources. Vertical splitting is not supported.
A migration task for a PolarDB-X 1.0 instance is a distributed migration. A subtask is created for each RDS MySQL instance mounted to the PolarDB-X 1.0 instance. You can view the status of subtasks in the 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 disrupted, such as in a disaster recovery scenario for the incremental data collection 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 migrate data, evaluate the performance of the source and destination databases. We recommend that you perform data migration during off-peak hours. Initial full data synchronization consumes read and write resources of the source and destination databases, which may increase the database load.
Initial full data synchronization runs concurrent INSERT operations. This causes table fragmentation in the destination database. As a result, the tablespace of the destination instance is larger than that of the source instance.
During DTS migration, do not write data to the destination database from sources other than DTS. Otherwise, data inconsistency occurs between the source and destination databases.
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	Data transfer cost
Schema migration and full data migration	Free of charge.	Free of charge for this scenario.
Incremental data migration	Charged. For more information, see Billing overview.	Free of charge for this scenario.

SQL operations supported for incremental migration

Operation type	SQL operations
DML	INSERT, UPDATE, and 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 migration	Incremental migration
Source PolarDB-X 1.0 instance	SELECT permission	SELECT permission	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 with the RDS_SUPERUSER permissions.

To create a database account and grant permissions:

For a PolarDB-X 1.0 instance, see Account Management.
For an AnalyticDB for PostgreSQL instance, see Create and manage users and User permission management.

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	Configuration	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 shows how to migrate data between instances that belong to 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 more information about the permission requirements, 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 is used to receive the migrated objects.
	Database Account	Enter the database account of the destination AnalyticDB for PostgreSQL instance. For more information about the permission requirements, 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.

Configuration	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 tables as the migration objects. If you select an entire database, changes such as adding or deleting tables in that database are not migrated to the destination database.
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, the migration of other objects that depend on the mapped object may fail. To filter data using a WHERE clause, right-click the table that you want to migrate in the Selected Objects box and set a filter condition in the dialog box that appears. For more information, see Set a filter condition.

Click Next: Advanced Settings to configure advanced parameters.

Configuration	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 notifications. 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. In this example, you do not need to select a tag.
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.

Optional: After you complete the preceding configurations, click Next: Configure Database and Table Fields to set the Type, Primary Key Column, and Distribution Key for the migrated tables in the destination AnalyticDB for PostgreSQL instance.
Note
- This step is available only if you select Schema Migration for Migration Types when you configure the task objects. You can set Definition Status to All and then make the required modifications.
- You can select multiple columns to form a composite primary key for Primary Key Column. You must select one or more columns from the Primary Key Column as the Distribution Key. For more information, see Table management and 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.