Remove your barriers to Cloud: Attack the legacy mainframe monolith

BrandPost By Hemant Ahire & Stefan Aulbach
Sep 22, 2021
Cloud Computing

This article pinpoints the business and technology imperatives that are driving the need for legacy application migration and modernization from mainframe to AWS Cloud platform.

Credit: AWS

World leading enterprise organizations across every industry are driving towards a broader digital transformation agenda that is sponsored by their top leadership. Over the last decade, Cloud computing has been the driving technology that has delivered business value and competitive advantage to customers by leveraging key capabilities such as innovation, flexibility, productivity, agility, security, resiliency, cost optimizations, and risk mitigation. This article pinpoints the business and technology imperatives that are driving the need for legacy application migration and modernization from mainframe to AWS Cloud platform.


For up to 6 decades, mainframe systems have been the central nervous system for global enterprises and Fortune 500 companies across all industries. They deliver reliability, scalability, performance and security while processing tens of billions of business transactions every day for workloads ranging from credit card transactions, stock trades, money transfers to manufacturing processes or ERP systems. According to an estimate by IBM, “there are over 220 billion lines of COBOL in existence, a figure which equates to around 80% of the world’s actively used code and Mainframes process over 30 billion business transactions per day”.

Companies of all sizes ranging from startups to huge enterprise organizations have embraced Cloud computing to digitize their business models over the last five to ten years. Business-centric, innovation-led technology strategy spearheaded by C-Suite executive leaders has evolved to a point where a majority of these organizations are running some percentage of their overall IT portfolio on cloud platforms that are run by hyperscalers such as Amazon Web Services (AWS).

The challenge and business imperative

In many companies mainframe systems are still the heart of enterprise data processing. However, mainframe workloads pose a challenge when migrating to the cloud due to nature of its size, scale, scope, complexity, and legacy monolithic technologies—usually with technical debt and limited or lack of documentation. At the same time, companies are facing challenges due to an aging workforce that is skilled in mainframe technologies running on legacy programming languages like COBOL/DB2, PL/I, CA:GEN, NATURAL/ADABAS and Assembler applications. Nevertheless, there is a resistance to change them due to the risk involved in the event of any downtime which deter these organization from leveraging cloud-native modern technologies such as serverless, microservices and containers.

Ultimately, these organizations are looking to increasing the value of their IT landscape, by introducing agile development techniques, lowering complexity, and leveraging modern technologies, such as AI/ML. At the end of the day, a successful modernization uncovers the treasures from the legacy world, like data in VSAM, flat files and IMS, and provides modern and sustainable ways of using them.

Unleash Information

Mainframe data has decades of historical business transactions for massive amounts of users which can be leveraged to create new business capabilities that can benefit the organization and their customers. However, the mainframe’s strict separation between online and batch processing negatively impacts the business: the most accurate data is only present moments after the batch runs—with a delay in the range of hours or days.

To unlock the potential of this data, legacy data format (like VSAM) can be mapped to a relational data store such as Amazon Aurora. AWS also provides services for the full data life-cycle, e.g., ingestion (Amazon Kinesis); storage (Amazon S3, Amazon DynamoDB); processing and analysis (Amazon EMR); visualization (Amazon QuickSight); and automation (Amazon Data Pipeline). In a second step, clients can gain faster analytics capabilities using AWS’s big data services, such as AWS Lake Formation, which gives clients better insight into core business data originating from their mainframe and empowering businesses across various functions such as sales, marketing, revenue, and fraud detection.

Deloitte’s expertise in modernizing batch-heavy, legacy applications to real-time applications, and AWS’s platform allows for one of the most disruptive business transformations: always up-to-date and accurate information, which is one example of the added values modern architectures and modern environments can offer.

“Standing still” is not an option

Due to the challenges, large organizations have to overcome the risk-averse mindset and are faced with decision of migrating and modernizing their mainframe applications to Cloud. The notion of “standing still” will be counter-productive for these organizations and put them at a significant disadvantage from a competitive standpoint in the marketplace.

As an example, fintech startups entered the market to compete with traditional banking and financial service providers. They disrupt the consumer banking business model by launching 100% online, digitally powered systems. Moreover, data collection, aggregation and analytics efforts enable fraud detection and simultaneously support their sales teams. These are just some examples of competitive advantages for benefit of consumers by use of technology architectural assets (like apps, algorithms). When it comes to legacy banks, they can achieve similar capabilities post migration to AWS by taking advantage of their financial clout and skilled workforce, however speed will be of critical importance in delivering business value to their customers.

Powerful partnership to accelerate mainframe migration and modernization

AWS and Deloitte’s partnership combines the power and experience of two market leaders to accelerate the mainframe to cloud journey for their clients. Deloitte’s Mainframe Modernization Offering is part of the broader Application Modernization & Migration Offering (AMM) taking all legacy systems into consideration. Deloitte’s integrated capabilities help their customers define a strategy, maximize technical and operational benefits, help with preparing the workforce of the future, navigate regulatory and tax implications, and safely and reliably move away from monolithic, hard to maintain structures to modern Cloud Native environments.

The technology imperative behind mainframe migrations and modernizations

The above challenges with data management and complex code form a perfect storm of risk and high cost. Also from a strategic perspective, lacking agility with long development cycles introduce competitive disadvantages and hinders growth for a long time. The desire to deliver modern end-user experiences, to operate on a sustainable technology stack embracing Cloud technologies, and to reduce costs of expensive mainframe environments are other drivers for an updated application portfolio.

Update Non-Functional Requirements

When enterprises decide to move away from the mainframe, so-called Non-Functional Requirements (NFR), like reliability, availability, scalability, or security—aspects that are associated with mainframes for decades—must also be available on the new platform. AWS has developed the “AWS Well-Architected Framework” that covers these aspects and provide guidelines for safely moving workloads into AWS, operating various environments, and leverage the Cloud’s unique benefits such as elastic infrastructure and pay-as-you-go model.

As the only partner with AWS Mainframe Competency for Consulting & Technology, Deloitte has a proven record of applying the AWS Well Architected Framework. As an example, the State of Utah Department of Human Services (DHS) wanted to modernize their legacy Child Support application to improve the benefits and usability for their citizens. The current technology stack was limiting the ability to change business processes and scale. Using Deloitte’s automated transformation capabilities—in this case from COBOL to Java—2.5M lines of code and 2 TB of DB2 data were being moved into AWS GovCloud.

Leverage Platform Services

Applying the AWS Well Architected Framework is facilitated by leveraging modern operations with AWS Shared Services Platform (SSP). It offers solutions for cross-functional aspects, such as CI/CD pipelines, security, logging and audit, identity management, monitoring, governance, and load balancing. In contrast to the rather static service landscape of mainframe systems, developers can leverage much more flexibility in using these services. Rather than waiting for services to be provisioned, they can provision these services instantly by themselves. The shared responsibility model ensures that customer policies are immediately in place for safe deployment. With SSP, AWS allows for modern development and operations, further reducing development and deployment efforts.

Think Cloud Native

A Cloud Native Environment is capable of abstracting away the non-functional requirements of the underlying services. AWS Managed services, deployed at each individual layer of an application, provide instant resource availability based on workload demands. The workloads can be distributed based on expected resource utilization, leveraging elastic environments which allow for dynamic adoption to increasing or decreasing resource requirements. Moreover, serverless computing enables “scale to zero”, where an application is automatically hibernated once it is no longer required. This is an important improvement, as mainframe hardware requires to be scaled for peak-load, often required only at certain point in times.


New trends are emerging everywhere and disrupt the way we do business. In such a setting, technology is responsible for supporting the business, and must not slow down the development of innovative business models and new ideas. Monolithic, legacy applications are one reason for a non-competitive time-to-market. In addition maintaining outdated programming languages and paradigms will become more and more difficult.

With the unique partnership of Deloitte and AWS, it is possible to solve the challenges with successful proven application modernization approaches to get rid of these blocking factors. Focusing on scalability at all levels, this way of application modernization enables business stakeholders, development and deployment teams to keep up with the pace and produce scalable applications supporting the present and future business of our customers ranging from small in-house applications to planet-scale, customer-facing platforms.