Migrate to Azure SQL Database

Introduction to Azure SQL Database Migration

Migrating your on-premises SQL Server databases to Azure SQL Database offers numerous benefits, including enhanced scalability, high availability, robust security features, and reduced operational overhead. This tutorial provides a comprehensive guide to planning, executing, and validating your migration process.

Key Benefits of Azure SQL Database:

• Scalability: Dynamically scale compute and storage resources up or down as needed.
• High Availability: Built-in redundancy and automated backups ensure your data is always accessible.
• Managed Service: Microsoft handles patching, updates, and infrastructure maintenance.
• Security: Advanced threat protection, transparent data encryption, and granular access control.
• Cost-Effectiveness: Pay only for what you use and leverage reserved instances for cost savings.

Migration Strategies

Azure provides several migration strategies to suit different scenarios:

1. Online Migration:

This method minimizes downtime by continuously synchronizing data from the source to the target Azure SQL Database. Ideal for mission-critical applications with low downtime tolerance.

• Tools: Azure Database Migration Service (DMS), Transactional Replication.

2. Offline Migration:

This approach involves taking the source database offline, migrating the data, and then bringing the Azure SQL Database online. Suitable for applications that can tolerate a scheduled downtime window.

• Tools: BACPAC files, Azure Data Factory, SQL Server Management Studio (SSMS) Import/Export Wizard.

Pre-Migration Assessment

A thorough assessment is the cornerstone of a successful migration. Use the following tools and steps:

Using Azure Migrate:

Azure Migrate is a centralized hub for discovering, assessing, and migrating on-premises applications and servers to Azure. It provides:

• Discovery: Inventory your servers and databases.
• Assessment: Analyze compatibility and estimate Azure costs.
• Readiness: Identify potential migration blockers.

Using Data Migration Assistant (DMA):

DMA helps you identify feature parity issues and provides recommendations for refactoring your on-premises SQL Server databases for Azure SQL Database. It can:

• Detect breaking changes.
• Detect unsupported features.
• Detect behavior changes.

Download DMA from the Microsoft Download Center.

Using SQL Server Management Studio (SSMS):

SSMS can also perform basic assessments, particularly for generating migration scripts and checking compatibility at a high level.

Migration Steps with Azure Database Migration Service (DMS)

This section details a typical online migration using Azure DMS.

Step 1: Prepare Your Source and Target Environments

Ensure your source SQL Server is accessible and that you have created an Azure SQL Database instance. For online migrations, ensure network connectivity between your on-premises environment and Azure.

Step 2: Create an Azure Database Migration Service Instance

In the Azure portal, search for "Azure Database Migration Service" and create a new instance. Choose an appropriate pricing tier and configure networking.

Step 3: Create a Migration Project

Within your DMS instance, create a new migration project. Select "SQL Server to Azure SQL Database" as the source and target, and choose your migration type (e.g., Online data migration).

Step 4: Configure Source and Target Details

Provide the connection details for your source SQL Server and your target Azure SQL Database. You'll need server names, authentication credentials, and database names.

Step 5: Select Databases and Objects

Choose the specific databases and objects you wish to migrate.

Step 6: Configure Migration Settings

Specify any advanced settings, such as tables to exclude or performance tuning options.

Step 7: Run the Migration

Start the migration process. DMS will begin copying the schema and data. For online migrations, it will set up continuous synchronization.

-- Example SQL for creating a target Azure SQL Database
CREATE DATABASE MyAzureSQLDB
MODIFY NAME = MyAzureSQLDB;
GO

ALTER DATABASE MyAzureSQLDB
MODIFY (EDITION = 'Standard', SERVICE_OBJECTIVE = 'S1'); -- Adjust as needed
GO
                        

Step 8: Monitor the Migration

Use the DMS portal to monitor the progress, status, and any errors during the migration. You can see the migration status of each database, data transfer rates, and validation checks.

Post-Migration Validation and Cutover

Once the initial data load is complete and synchronization is running (for online migrations), it's time to validate and perform the cutover.

Validation Steps:

• Data Integrity: Compare row counts between source and target tables. Run sample queries on both to ensure data consistency.
• Schema Validation: Verify that all necessary objects (tables, views, stored procedures, functions) have been migrated correctly.
• Application Testing: Connect your applications to the Azure SQL Database and perform thorough functional testing. Check performance metrics.

Cutover Process (Online Migration):

1. Stop Source Writes: Briefly stop all application writes to the source database.
2. Ensure Synchronization: Wait for DMS to apply any remaining transaction logs to the target Azure SQL Database.
3. Perform Final Validation: A quick final check of data consistency.
4. Redirect Applications: Update connection strings in your applications to point to the Azure SQL Database.
5. Resume Application: Start your applications, now connected to Azure SQL Database.
6. Decommission Source: Once you are confident in the migration, you can decommission the source SQL Server.

Best Practices for Azure SQL Database Migration

• Plan thoroughly: Don't rush the assessment and planning phases.
• Start small: Consider migrating a non-critical database first to gain experience.
• Test, test, test: Rigorous testing is paramount before and after cutover.
• Monitor performance: Continuously monitor the performance of your Azure SQL Database and adjust resources as needed.
• Secure your data: Implement Azure SQL Database security best practices, including firewall rules, VNet integration, and auditing.
• Optimize costs: Explore different service tiers and purchasing options (e.g., reserved instances) to optimize your spending.
• Backup and disaster recovery: Understand Azure SQL Database's automated backup capabilities and configure your disaster recovery strategy.