Today, mainframes continue to play a strategic role in the IT logic of many organizations. There are many complex legacy systems that are there to work as a single data store or a core business engine for multiple business platforms. New business scenarios demand them to be exposed on the web for SMAC (Social, Mobile, Cloud, and Analytics) platform usage. It is challenging and risky to touch the system keeping all the business items, as it is to cater to new business demands. API enablement helps here to unlock the data and expose it to new business needs. All of this can be done without having to reinvent the whole system.

Here we find the four basic steps for rapid API enablement:

1.  Connect to a legacy application using a noninvasive and sophisticated connector that supports all flavors of the mainframe system.

2. Model and parse the legacy application, using a specialized, modern design tool so that risk is reduced.

3. Expose standards-based granular services from the legacy application, which allows for easy reuse.

4. Use a good orchestration tool to build governing processes that invoke granular services and ensure long-term safety using current best-practice technologies.

The above picture depicts the four steps mentioned before. A custom connector will be used as required. For example, an RPC Connector would be used if we need to expose an MF business layer into API.

Benefits of API Enablement Compared to Other Ways for Legacy Modernization

1. Helps to grow a customer base by attracting customers to products and services through API ecosystems.

2. Avoids high amounts of risk easily, as no change is required on the legacy side.

3. Drives innovation by capitalizing on the composition of different APIs, whether company-built or third party.
4. Saves time compared to rewrite mechanism.
5. Improves integration capabilities.
6. Opens up more possibilities for a new era of computing and prepares for a flexible future.
7. Eases cloud enablement.

There are different tools available in the market like HATS (IBM Tool) and Openlegacy, which extend critical terminal applications to the web, mobile, portal, or as standard SOAP or RESTful web services without touching the existing application. No rewriting, refactoring, or access to application source code is required. This low-risk transformation can reduce training costs, increase end-user productivity and satisfaction, and enable the reuse of proven business logic in new applications.

These tools have multiple connectors for maximum flavors of a mainframe system, which are internally capable of doing automatic scanning and parsing business logic / green screens / databases to gather data and metadata with very little effort. This connector parses the program source code to find the exact data structure needed for activation; it takes care of data type conversions and creates a strong type entity, which maps and abstracts calls to that program as APIs.