Ensure the coexistence of your mainframe applications and the web! Three strategies to achieve a progressive migration of your legacy applications

In order to answer new business needs, many companies hosting legacy applications on a mainframe are considering a migration to open environments. Others choose to maintain the data on the mainframe and to modernize the applications developed around it, rewriting the latter as web applications.

In both cases, the mainframe hosts a huge amount of data which can rise to millions of lines of code. That is why such projects have to be planned over the long term. The rewriting has to be progressive, code portion after code portion, making the project last from 5 to 10 years.
To avoid generating useless overhead costs and putting the company’s activity on hold, the integration between the two worlds must be made without modifying the existing code, in order to remain simple and quick to implement .

Depending on the chosen modernization strategy, three strategies are possible : the newly developed applications can simply call-up the needed data on the mainframe; they can directly include existing 3270 screens, or they can use 3270 screens that have been beforehand modernized.

Integrating mainframe transactions’ data and results into new web applications

In this first case, new applications simply need to access mainframe data, either stored in a DB2 database for example, or resulting from an IMS or CICS transaction. You just need to get the data transferred and integrated into the new application: a JSON or XML web service can handle such an operation in a simple and non intrusive way.

Let’s study the case of a big transport company with critical business applications managed by a System z platform for several decades. Wanting to expand onto new markets, their mainframe applications need to evolve as quickly as possible to open the platform to a new user population. The project planned to last for around 10 years, the company needed to find a flexible solution allowing them to be quickly competitive.
The company chose to migrate the business application towards a web environment, while incorporating the ability to get data and transaction results directly from the mainframe. To do so, the application invokes the mainframe code through a JSON web service, which operates automatically on the mainframe and returns exclusively the data needed by the application. Set up in one day only, this solution doesn’t require any modification of the application, nor any specialized competence. Scalable and transparent for the new users (who only use the new web application), this solution gradually enables a complete switch towards the new platform, without impacting the business logic.

Integrating 3270 mainframe screens into new web applications

In the second case, the challenge is to enable the co-existence of both the web and mainframe worlds, while integrating 3270 screens within web applications. Indeed, users of migrated applications sometimes need to interact with programs which are still mainframe-managed; new applications must then call the mainframe via web services, and display a series of 3270 screens within the GUI.

This solution was chosen by an important banking institution, engaged in the rewriting of a business application. While the code still hosted on the mainframe is running, the new application triggers a web service presenting the required 3270 screens. Therefore, users get to use a unique workstation and see within their interface the screens they’re familiar with, no longer needing any old terminal. In the long term, the central transaction monitor will be removed in a transparent way for users, keeping only the data.

Integrating modernized mainframe screens into new web applications

In this last case, the challenge is the same as in the previous one, but the company wishes to modernize the mainframe-issued screens to harmonize their ergonomics. The solution is then to convert 3270 screens into rich graphical user interfaces (GUI) behaving like web pages, without ever altering the underlying code.

3270 screens modernization
3270 screen modernized according to different display-styles & devices

This approach was privileged by an important banking company having rewritten a part of their mainframe assets in the form of new web applications : they wanted to quickly integrate within them data and screens coming from their System z platform, avoiding any impact on users and any redevelopment on the new environment.
Converting 3270 screens into full HTML pages, compliant with the new applications graphics, allowed the company to save a considerable amount of time : no need to train (new) staff to 3270 requirements. This solution is thus economically much more profitable than the application-rewriting process.
The solution is therefore to convert 3270 screens into HTML pages which take back the new applications’ chart. It doesn’t require any training on the 3270 interface which saves a tremendous amount of time compared to a rewriting solution. This solution is economically much more profitable and faster than an application rewrite

Thanks to these three approaches, the migration of mainframe applications towards the new web technologies can be implemented in a secure, fast and progressive way. In any case, whatever the context and objectives, users are definitely undisturbed, training needs are very limited; the migration is performed without any mainframe-level modification, significantly limiting the costs the process involves.