MGN Migration for On-prem VM hosting both application and database

When migrating VMs that host both applications and databases using AWS Application Migration Service (MGN), there are several important considerations to address your concerns:

Regarding Crash-Consistent Replication and Database Integrity:

AWS MGN performs continuous block-level replication of source servers. While the service handles data replication efficiently, the crash-consistent nature of the replication means that databases may require recovery processes upon first boot in the target environment. This is similar to what would happen if a database server experienced an unexpected shutdown.

Controlled Cutover Approach:

A controlled cutover where you stop application and database services before the final cutover is indeed a recommended approach. You can schedule a migration cutover window during which you prevent user connectivity to the source environment, ensure all services are properly shut down, and then proceed with creating the final version of target machines. This approach helps ensure that all data is fully replicated and reduces the risk of database inconsistencies.

Alternatively, you can shut down source servers before the cutover phase to ensure no changes occur on the source servers and that all latest data is replicated to the target servers, as the data would be fully replicated to the staging area.

Testing and Validation:

Before proceeding with the final cutover, it's crucial to perform thorough testing. Once server replication is complete, you should create test target machines and confirm their functionality and accessibility. This includes validating that databases start properly and that application connectivity works as expected. Engage with business and application owners for acceptance tests, and if corrections are required, you can modify the target configurations and repeat testing.

Best Practices:

• Plan your migration in waves, grouping servers logically to minimize disruption
• Conduct comprehensive testing in an isolated environment before the production cutover
• Schedule adequate maintenance windows for the cutover process
• Validate database integrity and application functionality thoroughly in the test environment
• Ensure you have proper backup and rollback procedures in place

The testing phase is particularly important for database workloads, as it allows you to identify and address any recovery requirements or configuration adjustments needed in the AWS environment before committing to the final migration.
Sources
Accelerate Migrations to AWS with Tech Mahindra and AWS Application Migration Service | AWS Partner Network (APN) Blog
Simplify server migration to AWS with AWS Transform for VMware | Migration & Modernization
Migrating Oracle E-Business Suite using AWS Application Migration Service - Migrating Oracle E-Business Suite on AWS