Enterprises have invested much time and money in legacy systems. According to industry analysts, over 70% of the world's data is contained in legacy systems. IBM states that there are currently more transactions processed by CICS (IBM's Customer Information Control System) systems today than by the entire Internet. CICS handles more than 30 billion transactions per day, and is used by 492 of the Fortune 500.
Nine out of 10 ATM transactions are done using COBOL. IT departments in large corporations manage over 30,000 CICS code modules written in COBOL, Assembler, or PL/I. The oldest modules are 25-30 years old, but still process mission-critical data every day and almost certainly will continue to run for years to come. You get the idea - legacy systems still have an important role to play in business today.
This enormous amount of code, running on mainframe and AS/400 systems, is collectively known as "legacy applications." Between 70-80% of IT budgets is spent yearly to maintain and evolve this code.
Many corporate IT departments have turned to Windows and Unix-based machines to complement their existing mainframes for developing and deploying Web and composite applications. The mission-critical legacy applications residing on the mainframe must be leveraged to provide both data and business logic to power these new Web and composite applications. It is too costly to simply recode legacy applications in languages designed for these new platforms.
Legacy application integration is the solution. Existing legacy applications must be made available to these new Web and composite applications. Corporate IT departments must be able to isolate specific business transactions from within one or more applications and expose them on the Web or create composite applications. Web services is the technology powering this new form of application integration.
The challenge lies in how to provide Web services from existing legacy applications - without relying on terminal emulation. The traditional approach to legacy connection has been through emulation. In the past 12-18 months, emulation-based products have emerged that can provide Web services from underlying host transactions. While this is a major step forward, the need still exists for high-performance integration with the host. ClientSoft has pioneered a new breed of legacy integration tools to provide "direct integration" with mainframe applications. This direct integration approach allows the creation of Web services that interact with existing mainframe applications, without relying on terminal emulation.
The "Screen Scraping" Image
In the early 1990s, emulation-based technology was in its infancy and was characterized as "screen scraping." Screen scraping is the process of taking the data from the screens of a legacy program that was formatted for a "green-screen" terminal, and reformatting the data for use in a new user interface. The input from the new interface must also be reformatted to allow the underlying legacy program to understand the request. Screen scraping became a derogatory term. However, at the time using the data stream in a screen scraping project was the only surefire way to access legacy transactions.
