Data Transmission Service:Migrate data from a self-managed PostgreSQL database to an RDS for PostgreSQL instance

Prerequisites

• Create a destination RDS for PostgreSQL instance with more storage space than the source self-managed PostgreSQL database. For more information about creating an RDS for PostgreSQL instance, see Create an RDS for PostgreSQL instance.

  Note

  • For information about the supported versions of the source and destination databases, see Overview of migration solutions.

  • 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.

• Create a database in the destination RDS for PostgreSQL instance to store the migrated data. For more information, see Create a database.

Precautions

Migration types

• Schema migration

  DTS migrates the schema definitions of the migration objects from the source database to the destination database.

  Note

  DTS supports schema migration for the following types of objects: tables, triggers, views, sequences, functions, user-defined types, rules, domains, operations, and aggregates.

• Full migration

  DTS migrates all historical data of the specified migration objects from the source database to the destination database.

• Incremental migration

  After a full migration is complete, DTS migrates incremental data updates from the source database to the destination database. Incremental migration lets you smoothly migrate data without interrupting your self-managed applications.

Supported objects for migration

• SCHEMA and TABLE.

  Note

  This includes PRIMARY KEY, UNIQUE KEY, FOREIGN KEY, DATATYPE (built-in data types), and DEFAULT CONSTRAINT.

• VIEW, PROCEDURE (for PostgreSQL 11 or later), FUNCTION, RULE, SEQUENCE, EXTENSION, TRIGGER, AGGREGATE, INDEX, OPERATOR, and DOMAIN.

SQL operations that support incremental migration

Permissions required for database accounts

To create a database account and grant permissions:

• For a self-managed PostgreSQL database, see the CREATE USER and GRANT syntax.

• For an RDS for PostgreSQL instance, see Create an account.

Preparations

Perform the following preparations for all versions of a self-managed PostgreSQL database.

1. Log on to the server that hosts the self-managed PostgreSQL database.

2. Run the following command to query the number of used replication slots in the database.

   select count(1) from pg_replication_slots;

3. Modify the postgresql.conf file. Set the wal_level parameter to logical. Ensure that the values of the max_wal_senders and max_replication_slots parameters are greater than the sum of the used replication slots and the number of DTS instances that will use this self-managed PostgreSQL database as the source.

   # - Settings -
   
   wal_level = logical			# minimal, replica, or logical
   					# (change requires restart)
   
   ......
   
   # - Sending Server(s) -
   
   # Set these on the master and on any standby that will send replication data.
   
   max_wal_senders = 10		# max number of walsender processes
   				# (change requires restart)
   #wal_keep_segments = 0		# in logfile segments, 16MB each; 0 disables
   #wal_sender_timeout = 60s	# in milliseconds; 0 disables
   
   max_replication_slots = 10	# max number of replication slots
   				# (change requires restart)

   Note

   After you modify the configuration file, restart the self-managed PostgreSQL database for the parameter settings to take effect.

4. Add the IP addresses of the DTS servers to the pg_hba.conf configuration file of the self-managed PostgreSQL database. Add only the IP address CIDR blocks for the DTS servers that are in the same region as the destination database. For more information, see Add the CIDR blocks of DTS servers to the whitelist of a database.

   Note

   • After you modify the configuration file, run the SELECT pg_reload_conf(); command or restart the self-managed PostgreSQL database for the parameter settings to take effect.

   • For more information about the settings of this configuration file, see The pg_hba.conf File. If you have configured the trusted address as 0.0.0.0/0 (as shown in the following figure), you can skip this step.

   

5. Based on the database and schema information of the objects to be migrated, create the corresponding database and schema in the destination RDS for PostgreSQL instance. The schema names must be the same. For more information, see Create a database and Manage schemas.

If the version of your self-managed PostgreSQL database is from 9.4.8 to 10.0, you must also perform the following preparations.

1. Download the PostgreSQL source code, and then compile and install it.

   1. Download the source code that corresponds to the version of your source self-managed PostgreSQL database from the PostgreSQL official website.

   2. Run the sudo ./configure, sudo make, and sudo make install commands in sequence to configure, compile, and install the source code.

      Important

      • When you compile and install PostgreSQL, the operating system version must be compatible with the GCC (GNU Compiler Collection) version.

      • If an error occurs when you run the sudo ./configure command, you can modify the command based on the error message. For example, if the error message is readline library not found. Use --without-readline to disable readline support., you can change the command to sudo ./configure --without-readline.

      • If you installed PostgreSQL using another method, you must compile the ali_decoding plugin in a staging environment that has the same operating system and GCC version as your production environment.

2. Download the ali_decoding plugin provided by DTS, and then compile and install it.

   1. Download ali_decoding.

   2. Copy the entire ali_decoding directory to the `contrib` directory of the compiled and installed PostgreSQL source code.

      

   3. Go to the ali_decoding directory and replace the content of the `Makefile` file with the following script:

      # contrib/ali_decoding/Makefile
      MODULE_big = ali_decoding
      MODULES = ali_decoding
      OBJS    = ali_decoding.o
      
      DATA = ali_decoding--0.0.1.sql ali_decoding--unpackaged--0.0.1.sql
      
      EXTENSION = ali_decoding
      
      NAME = ali_decoding
      
      #subdir = contrib/ali_decoding
      #top_builddir = ../..
      #include $(top_builddir)/src/Makefile.global
      #include $(top_srcdir)/contrib/contrib-global.mk
      
      #PG_CONFIG = /usr/pgsql-9.6/bin/pg_config
      #pgsql_lib_dir := $(shell $(PG_CONFIG) --libdir)
      #PGXS := $(shell $(PG_CONFIG) --pgxs)
      #include $(PGXS)
      
      # Use the following for source code installation
      ifdef USE_PGXS
      PG_CONFIG = pg_config
      PGXS := $(shell $(PG_CONFIG) --pgxs)
      include $(PGXS)
      else
      subdir = contrib/ali_decoding
      top_builddir = ../..
      include $(top_builddir)/src/Makefile.global
      include $(top_srcdir)/contrib/contrib-global.mk
      endif

   4. Go to the ali_decoding directory. Run the sudo make and sudo make install commands in sequence to compile the ali_decoding plugin and retrieve the files required for installation.

   5. Copy the following files to the specified locations.

      

3. Based on the database and schema information of the objects to be migrated, create the corresponding database and schema in the destination RDS for PostgreSQL instance. The schema names must be the same. For more information, see Create a database and Manage schemas.

Procedure

1. 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.

2. Click Create Task to navigate to the task configuration page.

3. 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 PostgreSQL.
   	Connection Type	Select a connection type based on the deployment location of the source database. This topic uses Cloud Enterprise Network (CEN) as an example. Note If the source instance is a self-managed database, you must also perform the necessary preparations. For more information, see Preparations.
   	Instance Region	Select the region where the self-managed PostgreSQL database is located.
   	CEN Instance ID	Select the ID of the CEN instance to which the self-managed PostgreSQL database belongs.
   	VPC Connected to Database	Select the VPC that is connected to the self-managed PostgreSQL database.
   	Domain Name or IP Address	Enter the IP address of the server that hosts the self-managed PostgreSQL database.
   	Port	Enter the service port of the self-managed PostgreSQL database. The default value is 5432.
   	Database Name	Enter the name of the database in the self-managed PostgreSQL instance that contains the objects to be migrated.
   	Database Account	Enter the database account for the self-managed PostgreSQL database. For information about the required permissions, see Permissions required for database accounts.
   	Database Password	Enter the password for the database account.
   	Encryption	Select Non-encrypted for this example. To use SSL encryption, select SSL-encrypted and upload the CA Certificate. If using a client certificate, also upload the Client Certificate and Private Key of Client Certificate, and specify the Private Key Password of Client Certificate. For SSL configuration on an ApsaraDB RDS instance, see SSL encryption.
   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.
   	Connection Type	Select Cloud Instance.
   	Instance Region	Select the region where the destination RDS for PostgreSQL instance is located.
   	Instance ID	Select the ID of the destination RDS for PostgreSQL instance.
   	Database Name	Enter the name of the database in the destination RDS for PostgreSQL instance that will receive the migrated objects.
   	Database Account	Enter the database account for the destination RDS for PostgreSQL instance. For information about the required permissions, see Permissions required for database accounts.
   	Database Password	Enter the password for the database account.
   	Encryption	Same SSL options as the source database.

4. 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.

5. Configure the task objects.

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

      Configuration	Description
      Migration Types	For full migration: select Schema Migration and Full Data Migration. For zero-downtime migration: select Schema Migration, Full Data Migration, and Incremental Data Migration. If you do not select Incremental Data Migration, do not write new data to the source during migration.
      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.
      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	Select objects from the Source Objects section and click the arrow icon to add them to Selected Objects. You can select at the schema or table level. Selecting tables does not migrate views, triggers, or stored procedures. If a table has a SERIAL field and you select Schema Migration, also select Sequence or migrate the entire schema.
      Selected Objects	To change the name of a single migration object in the destination instance, right-click the migration object in the Selected Objects box. For instructions, see Map a single database, table, or column name. To batch change the names of migration objects in the destination instance, in the upper-right corner of the Selected Objects box, click Batch Edit. For more information, see Batch Mapping for Database, 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 set a WHERE condition to filter data, right-click the table to be migrated in the Selected Objects box and set the filter condition in the dialog box that appears. For more information, see Set filter conditions. To select the SQL operations to be migrated at the database or table level, right-click the migration object in the Selected Objects box and select the desired SQL operations in the dialog box that appears.

   2. 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.
      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 as needed. For this topic, a selection is not required.
      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.

   3. Click Next: Data Validation to configure a data validation task.

      For more information about the data validation feature, see Configure data validation.

6. 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.

7. Purchase the instance.

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

   2. 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?
      	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.

   3. After the configuration is complete, read and select Data Transmission Service (Pay-as-you-go) Service Terms.

   4. 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.