Tutorial: Migrate/Upgrade Azure Database for PostgreSQL - Single Server to Azure Database for PostgreSQL - Single Server online using DMS via the Azure portal

You can use Azure Database Migration Service to migrate the databases from an Azure Database for PostgreSQL - Single Server instance to same or different version of Azure Database for PostgreSQL - Single Server instance or Azure Database for PostgreSQL - Flexible Server with minimal downtime. In this tutorial, you migrate the DVD Rental sample database from an Azure Database for PostgreSQL v10 to Azure Database for PostgreSQL - Single Server by using the online migration activity in Azure Database Migration Service.

In this tutorial, you learn how to:

Prerequisites

To complete this tutorial, you need to:

• Check status of migration scenarios supported by Azure Database Migration Service for supported migration and version combinations.

• An existing Azure Database for PostgreSQL version 10 and later instance with the DVD Rental database.

  Also note that the target Azure Database for PostgreSQL version must be equal to or later than the on-premises PostgreSQL version. For example, PostgreSQL 10 can migrate to Azure Database for PostgreSQL 10, or 11, but not to Azure Database for PostgreSQL 9.6.

• Create an Azure Database for PostgreSQL server or Create an Azure Database for PostgreSQL - Hyperscale (Citus) server as the target database server to migrate data into.

• Create an Azure Virtual Network for Azure Database Migration Service by using the Azure Resource Manager deployment model. For more information about creating a virtual network, see the Virtual Network Documentation, and especially the quickstart articles with step-by-step details.

• Ensure that the Network Security Group (NSG) rules for your virtual network don't block the outbound port 443 of ServiceTag for ServiceBus, Storage and AzureMonitor. For more detail on virtual network NSG traffic filtering, see the article Filter network traffic with network security groups.

• Create a server-level firewall rule for Azure Database for PostgreSQL source to allow Azure Database Migration Service to access to the source databases. Provide the subnet range of the virtual network used for Azure Database Migration Service.

• Create a server-level firewall rule for Azure Database for PostgreSQL target to allow Azure Database Migration Service to access to the target databases. Provide the subnet range of the virtual network used for Azure Database Migration Service.

• Enable logical replication in the Azure Database for PostgreSQL source.

• Set the following Server parameters in the Azure Database for PostgreSQL instance being used as a source:

  • max_replication_slots = [number of slots], recommend setting to ten slots
  • max_wal_senders =[number of concurrent tasks] - The max_wal_senders parameter sets the number of concurrent tasks that can run, recommend setting to 10 tasks

Migrate the sample schema

To complete all the database objects like table schemas, indexes and stored procedures, we need to extract schema from the source database and apply to the database.

1. Use pg_dump -s command to create a schema dump file for a database.

   pg_dump -O -h hostname -U db_username -d db_name -s > your_schema.sql
   

   For example, to create a schema dump file for the dvdrental database:

   pg_dump -O -h mypgserver-source.postgres.database.chinacloudapi.cn -U pguser@mypgserver-source -d dvdrental -s -x > dvdrentalSchema.sql
   

   For more information about using the pg_dump utility, see the examples in the pg-dump tutorial.

2. Create an empty database in your target environment, which is Azure Database for PostgreSQL.

   For details on how to connect and create a database, see the article Create an Azure Database for PostgreSQL server in the Azure portal or Create an Azure Database for PostgreSQL - Hyperscale (Citus) server in the Azure portal.

   Note

   An instance of Azure Database for PostgreSQL - Hyperscale (Citus) has only a single database: citus.

3. Import the schema into the target database you created by restoring the schema dump file.

   psql -h hostname -U db_username -d db_name < your_schema.sql
   

   For example:

   psql -h mypgserver-source.postgres.database.chinacloudapi.cn  -U pguser@mypgserver-source -d dvdrental citus < dvdrentalSchema.sql
   

   Note

   The migration service internally handles the enable/disable of foreign keys and triggers to ensure a reliable and robust data migration. As a result, you do not have to worry about making any modifications to the target database schema.

Register the resource provider

Register the Microsoft.DataMigration resource provider before you create your first instance of the Database Migration Service.

1. Sign in to the Azure portal. Search for and select Subscriptions.

   

2. Select the subscription in which you want to create the instance of Azure Database Migration Service, and then select Resource providers.

   

3. Search for migration, and then select Register for Microsoft.DataMigration.

   

Create a DMS instance

1. In the Azure portal, select + Create a resource, search for Azure Database Migration Service, and then select Azure Database Migration Service from the drop-down list.

   

2. On the Azure Database Migration Service screen, select Create.

   

3. On the Create Migration Service screen, specify a name, the subscription, a new or existing resource group, and the location for the service.

4. Select an existing virtual network or create a new one.

   The virtual network provides Azure Database Migration Service with access to the source PostgreSQL server and the target Azure Database for PostgreSQL instance.

   For more information about how to create a virtual network in the Azure portal, see the article Create a virtual network using the Azure portal.

5. Select a pricing tier.

   For more information on costs and pricing tiers, see the pricing page.

   

6. Select Review + create to create the service.

   Service creation will complete within about 10 to 15 minutes.

Create a migration project

After the service is created, locate it within the Azure portal, open it, and then create a new migration project.

1. In the Azure portal, select All services, search for Azure Database Migration Service, and then select Azure Database Migration Services.

   

2. On the Azure Database Migration Services screen, search for the name of Azure Database Migration Service instance that you created, select the instance, and then select + New Migration Project.

3. On the New migration project screen, specify a name for the project, in the Source server type text box, select PostgreSQL, in the Target server type text box, select Azure Database for PostgreSQL.

   Note

   Choose PostgreSQL in the Source server type even though the source server is an Azure Database for PostgreSQL instance.

4. In the Choose type of activity section, select Online data migration.

   

   Note

   Alternately, you can choose Create project only to create the migration project now and execute the migration later.

5. Select Save, note the requirements to successfully use Azure Database Migration Service to migrate data, and then select Create and run activity.

Specify source details

1. On the Add Source Details screen, specify the connection details for the source PostgreSQL instance.

   

   Note

   You can find details such as "Server name", "Server port", "Database name", etc. in the Azure Database for PostgreSQL portal.

2. Select Save.

Specify target details

1. On the Target details screen, specify the connection details for the target Hyperscale (Citus) server, which is the pre-provisioned instance of Hyperscale (Citus) to which the DVD Rentals schema was deployed by using pg_dump.

   

   Note

   You can migrate from an Azure Database for PostgreSQL instance to another Azure Database for PostgreSQL single-server instance or to a Hyperscale (Citus) server.

2. Select Save, and then on the Map to target databases screen, map the source and the target database for migration.

   If the target database contains the same database name as the source database, Azure Database Migration Service selects the target database by default.

   

3. Select Save, and then on the Migration settings screen, accept the default values.

   

4. Select Save, on the Migration summary screen, in the Activity name text box, specify a name for the migration activity, and then review the summary to ensure that the source and target details match what you previously specified.

   

Run the migration

• Select Run migration.

The migration activity window appears, and the Status of the activity should update to show as Backup in Progress. You may encounter the following error when upgrading from Azure Database for PostgreSQL 9.5 or 9.6:

A scenario reported an unknown error. 28000: no pg_hba.conf entry for replication connection from host "40.121.141.121", user "sr"

This is because the PostgreSQL does not have appropriate privileges to create required logical replication artifacts. To enable required privileges, you can do the following:

1. Open "Connection security" settings for the source Azure Database for PostgreSQL server you are trying to migrate/upgrade from.
2. Add a new firewall rule with a name ending with "_replrule" and add the IP address from the error message to the start IP and End IP fields. For the above error example -

Firewall rule name = sr_replrule; Start IP = 40.121.141.121; End IP = 40.121.141.121

3. Click save and let the change complete.
4. Retry DMS activity.

Monitor the migration

1. On the migration activity screen, select Refresh to update the display until the Status of the migration shows as Complete.

   

2. When the migration is complete, under Database Name, select a specific database to get to the migration status for Full data load and Incremental data sync operations.

   Note

   Full data load shows the initial load migration status, while Incremental data sync shows change data capture (CDC) status.

   

   

Perform migration cutover

After the initial Full load is completed, the databases are marked Ready to cutover.

1. When you're ready to complete the database migration, select Start Cutover.

2. Wait until the Pending changes counter shows 0 to ensure that all incoming transactions to the source database are stopped, select the Confirm checkbox, and then select Apply.

   

3. When the database migration status shows Completed, recreate sequences (if applicable), and connect your applications to the new target instance of Azure Database for PostgreSQL.

Next steps

• For information about known issues and limitations when performing online migrations to Azure Database for PostgreSQL, see the article Known issues and workarounds with Azure Database for PostgreSQL online migrations.
• For information about the Azure Database Migration Service, see the article What is the Azure Database Migration Service?.
• For information about Azure Database for PostgreSQL, see the article What is Azure Database for PostgreSQL?.