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Difficulty: HardAssess and Select Migration Strategy (7 Rs)

A financial services enterprise is planning to migrate its core application portfolio to AWS. The portfolio consists of three key components:

1. A monolithic Java application running on Apache Tomcat. The application code cannot be modified due to a strict 3-month migration window and a lack of Java development resources. However, the company wants to minimize server administration overhead on AWS.
2. A backend transactional database running on Oracle Database EE. To reduce ongoing operational expenditures, the executive leadership has mandated the complete elimination of proprietary database licensing costs. The migration team has been allocated a separate 9-month timeframe to perform comprehensive schema conversions and rewrite database-interacting application queries.
3. A legacy COBOL reporting system running on an aging mainframe. Due to compliance requirements, the historical ledger data must remain accessible once a year. The source code is lost, and the system cannot be simulated or migrated to the cloud.

Which combination of migration strategies under the 7 Rs framework should the solutions architect recommend to meet all requirements?

  1. A
    Rehost the Java application on Amazon EC2; Rehost the Oracle database to Amazon RDS for Oracle; Retire the legacy COBOL reporting system.
  2. B
    Replatform the Java application to Amazon ECS on AWS Fargate; Replatform the Oracle database by migrating it to Amazon Aurora PostgreSQL; Retain the legacy COBOL reporting system on-premises.
  3. Replatform the Java application to Amazon ECS on AWS Fargate; Refactor the Oracle database by converting the schema and migrating to Amazon Aurora PostgreSQL; Retain the legacy COBOL reporting system on-premises.Answer
  4. D
    Refactor the Java application by rewriting it into AWS Lambda functions; Refactor the Oracle database by migrating to Amazon Aurora PostgreSQL; Rehost the legacy COBOL reporting system using AWS Mainframe Modernization.

Answer

Replatform the Java application to Amazon ECS on AWS Fargate; Refactor the Oracle database by converting the schema and migrating to Amazon Aurora PostgreSQL; Retain the legacy COBOL reporting system on-premises.
The correct strategy combination aligns each application tier with its timeline and business constraints. The Java/Tomcat application is containerized and hosted on a serverless container platform (Amazon ECS on Fargate) without changes to the application code, which qualifies as Replatforming. The Oracle database is migrated to an open-source compatible engine (Amazon Aurora PostgreSQL), which requires schema conversion and query modifications, making this a Refactoring (or Re-architecting) strategy. The legacy COBOL mainframe system cannot be migrated or simulated due to compliance and technical constraints, so it must be kept in its current state on-premises, which represents Retaining.

Step-by-Step Solution

1
Analyze the constraints and goals of the Java/Tomcat tier.
The application must be migrated within 3 months, code cannot be changed, and management overhead must be minimized. Containerizing it and running on ECS Fargate without code modifications represents a Replatform strategy.
This yields cloud benefits (reduced management) without the time and resource investment of a code rewrite.
2
Analyze the database tier requirements and constraints.
Proprietary licensing costs must be eliminated, and a 9-month timeline is given for schema conversion and query rewrites. Migrating from Oracle to Amazon Aurora PostgreSQL requires schema conversion and query refactoring, representing a Refactoring (Re-architecting) strategy.
Engine changes require significant modification of database-interacting code and schemas, which falls under Refactoring.
3
Analyze the mainframe reporting tier requirements.
The system cannot be simulated or migrated, source code is lost, and it must remain accessible once a year for compliance. Keeping it on-premises represents a Retain strategy.
When an application cannot be migrated to the cloud and must remain active, Retain is the appropriate 7 Rs strategy.

Key Concept

Selecting the correct 7 Rs migration strategy (Rehost, Replatform, Refactor, Retain, Retire, Relocate, Repurchase) based on technical, timeline, and financial constraints.
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Assess and Select Migration Strategy (7 Rs)

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