This topic describes how to perform schema migration, full data migration, and incremental data migration between ApsaraDB RDS for PostgreSQL instances by using Data Transmission Service (DTS). When you migrate data between ApsaraDB RDS for PostgreSQL instances, you can select all supported migration types to ensure service continuity.
Prerequisites
The source and destination ApsaraDB RDS for PostgreSQL instances are created. For more information, see Create an instance.
NoteFor information about the supported versions of the source and destination databases, see Overview of data migration scenarios.
To ensure compatibility, the version of the destination database must be the same as or later than that of the source database. If the version of the destination database is earlier than that of the source database, database compatibility issues may occur.
The available storage space of the destination ApsaraDB RDS for PostgreSQL instance must be larger than the total size of data in the source ApsaraDB RDS for PostgreSQL instance.
Usage notes
Limit type | Description |
Limits on the source database |
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Other limits |
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Special cases | During data migration, do not modify the endpoint or zone of the source ApsaraDB RDS for PostgreSQL instance. Otherwise, the data migration task fails. |
Migration types
Schema migration
DTS migrates the schemas of the selected objects from the source database to the destination database.
Full data migration
DTS migrates the historical data of required objects from the source database to the destination database.
Incremental data migration
After full data migration is completed, DTS migrates incremental data from the source database to the destination database. Incremental data migration allows data to be migrated smoothly without interrupting the services of self-managed applications during data migration.
SQL operations that support incremental migration
Operation type | SQL statement |
DML | INSERT, UPDATE, and DELETE |
DDL |
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Permissions required for database accounts
Database type | Schema migration | Full data migration | Incremental data migration |
Source ApsaraDB RDS for PostgreSQL instance | The USAGE permission on the pg_catalog schema | The SELECT permission on the objects to be migrated | Permissions of a privileged account that is the owner of the database Note If the source ApsaraDB RDS for PostgreSQL instance runs PostgreSQL 9.4 and you want to migrate only DML operations, only the REPLICATION permission is required for the database account. |
Destination ApsaraDB RDS for PostgreSQL instance | The CREATE and USAGE permissions on the objects to be migrated | The permissions of the schema owner |
For more information about how to create a database account on an ApsaraDB RDS for PostgreSQL instance and grant permissions to the database account, see Create an account and Create a database.
Procedure
Go to the Data Migration page.
Log on to the Data Management (DMS) console.
In the top navigation bar, move the pointer over DTS.
Choose .
NoteThe actual operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.
You can also go to the Data Migration page of the new DTS console.
From the drop-down list on the right side of Data Migration Tasks, select the region in which your data migration instance resides.
NoteIf you use the new DTS console, you must select the region in which the data migration instance resides in the upper-left corner.
Click Create Task. On the Create Data Migration Task page, configure the source and destination databases. The following table describes the parameters.
WarningAfter you configure the source and destination databases, we recommend that you read the Limits that are displayed in the upper part of the page. Otherwise, the task may fail or data inconsistency may occur.
Section
Parameter
Description
N/A
Task Name
The name of the task. DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to specify a unique task name.
Source Database
Select an existing DMS database instance
The database instance that you want to use. You can choose whether to use an existing instance based on your business requirements.
If you select an existing instance, DTS automatically populates the parameters for the database.
If you do not select an existing instance, you must manually configure parameters for the database.
Database Type
The type of the source database. Select PostgreSQL.
Access Method
The access method of the source database. Select Alibaba Cloud Instance.
Instance Region
The region in which the source ApsaraDB RDS for PostgreSQL instance resides.
Instance ID
The ID of the source ApsaraDB RDS for PostgreSQL instance.
Database Name
The name of the database that contains the objects to be migrated from the source ApsaraDB RDS for PostgreSQL instance.
Database Account
The database account of the source ApsaraDB RDS for PostgreSQL instance. For information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
Database Password
The password that is used to access the database instance.
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.
NoteIf 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.
Destination Database
Select an existing DMS database instance
The database instance that you want to use. You can choose whether to use an existing instance based on your business requirements.
If you select an existing instance, DTS automatically populates the parameters for the database.
If you do not select an existing instance, you must manually configure parameters for the database.
Database Type
The type of the destination database. Select PostgreSQL.
Access Method
The access method of the destination database. Select Alibaba Cloud Instance.
Instance Region
The region in which the destination ApsaraDB RDS for PostgreSQL instance resides.
Instance ID
The ID of the destination ApsaraDB RDS for PostgreSQL instance.
Database Name
The name of the database to which objects are migrated in the destination ApsaraDB RDS for PostgreSQL instance.
Database Account
The database account of the destination ApsaraDB RDS for PostgreSQL instance. For information about the permissions that are required for the account, see the Permissions required for database accounts section of this topic.
Database Password
The password that is used to access the database instance.
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.
NoteIf 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.
In the lower part of the page, click Test Connectivity and Proceed.
If the source or destination database is an Alibaba Cloud database instance, such as an ApsaraDB RDS for MySQL or ApsaraDB for MongoDB instance, DTS automatically adds the CIDR blocks of DTS servers to the IP address whitelist of the instance. If the source or destination database is a self-managed database hosted on an Elastic Compute Service (ECS) instance, DTS automatically adds the CIDR blocks of DTS servers to the security group rules of the ECS instance, and you must make sure that the ECS instance can access the database. If the self-managed database is hosted on multiple ECS instances, you must manually add the CIDR blocks of DTS servers to the security group rules of each ECS instance. If the source or destination database is a self-managed database that is deployed in a data center or provided by a third-party cloud service provider, you must manually add the CIDR blocks of DTS servers to the IP address whitelist of the database to allow DTS to access the database. For more information, see the CIDR blocks of DTS servers section of the Add the CIDR blocks of DTS servers topic.
WarningIf the public CIDR blocks of DTS servers are automatically or manually added to the whitelist of a database instance or to the security group rules of an ECS instance, security risks may arise. Therefore, before you use DTS to migrate data, you must understand and acknowledge the potential risks and take preventive measures, including but not limited to the following measures: enhancing the security of your username and password, limiting the ports that are exposed, authenticating API calls, regularly checking the whitelist or security group rules and forbidding unauthorized CIDR blocks, or connecting the database instance to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.
Configure the objects to be migrated and advanced settings. The following table describes the parameters.
Parameter
Description
Migration Types
To perform only full data migration, select Schema Migration and Full Data Migration.
To migrate data without service downtime, select Schema Migration, Full Data Migration, and Incremental Data Migration.
NoteIf you select Schema Migration, DTS migrates the schemas of the tables to be migrated from the source database to the destination database. The schemas include foreign keys.
If you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
Processing Mode of Conflicting Tables
Precheck and Report Errors: checks whether the destination database contains tables that use the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started.
NoteIf the source and destination databases contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are migrated to the destination database. For more information, see Map object names.
Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.
WarningIf you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to the following potential risks:
If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database, the following scenarios may occur:
During full data migration, DTS does not migrate the data record to the destination database. The existing data record in the destination database is retained.
During incremental data migration, DTS migrates the data record to the destination database. The existing data record in the destination database is overwritten.
If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.
Source Objects
Select one or more objects from the Source Objects section. Click the icon to add the objects to the Selected Objects section.
NoteYou can select columns, tables, or schemas as the objects to be migrated. If you select tables or columns as the objects to be migrated, DTS does not migrate other objects, such as views, triggers, or stored procedures, to the destination database.
Selected Objects
- To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.
- To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.
NoteIf you use the object name mapping feature to rename an object, other objects that are dependent on the object may fail to be migrated.
To specify WHERE conditions to filter data, right-click a table in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Specify filter conditions.
To migrate SQL operations performed on a specific database or table, right-click the object in the Selected Objects section. In the dialog box that appears, select the SQL operations that you want to migrate. For more information about the SQL operations that support incremental migration, see the SQL operations that support incremental migration section of this topic.
Click Next: Advanced Settings to configure advanced settings.
Parameter
Description
Monitoring and Alerting
Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values:
No: does not configure alerting.
Yes: configures alerting. In this case, you must also configure the alert threshold and alert notification settings. For more information, see Configure monitoring and alerting when you create a DTS task.
Capitalization of Object Names in Destination Instance
The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.
Retry Time for Failed Connections
The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails.
NoteIf you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later takes precedence.
When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at the earliest opportunity after the source database and destination instance are released.
Retry Time for Other Issues
The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the change tracking task fails.
ImportantThe value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
Configure ETL
Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values:
Yes: configures the ETL feature. You can enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task.
No: does not configure the ETL feature.
In the lower part of the page, click Next: Save Task Settings and Precheck.
You can move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters to view the parameters to be specified when you call the relevant API operation to configure the DTS task.
NoteBefore you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.
If the task fails to pass the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.
If an alert is triggered for an item during the precheck:
If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.
If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.
Wait until Success Rate becomes 100%. Then, click Next: Purchase Instance.
On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.
Section
Parameter
Description
New Instance Class
Resource Group Settings
The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?
Instance Class
DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Specifications of data migration instances.
Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.
Click Buy and Start. In the dialog box that appears, click OK.
You can view the progress of the task in the task list.