The old (3270) and the new (Web services)
Many developers working on Web services applications may never have seen a
working IBM 3270 terminal with its pre-Windows PC display limited to bright
green phosphorous letters and numbers.
But they, along with their older COBOL brethren, still have to deal with 3270
issues when integrating legacy systems to Web applications, according to Jim
Rhyne, legacy modernization architect at IBM.
Rhyne said that while there aren't many 3270 terminals left, there are a lot
of mainframe applications still running that were originally designed for green
screen display. Web services may be ideal for the legacy integration, but there
may be performance issues on the mainframe to deal with, he added.
''I'll give you a quick classic case,'' said Rhyne. ''Let's say you have an
application that was originally written to drive a 3270 and support a
telemarketing group doing reservations. You now want to get onto the Web and
give more direct access to your customers and reduce costs. So what happens is
that you screen scrape the 3270 and put a Web front end on it; [you then] go out
onto the Web and get hit with 10 or 50 times the load that the original
application was designed for. All of a sudden your CICS back end or IMS back end
is crashing every hour because it's overloaded. I've actually seen this
The problem is that a developer working in the 1970s could not imagine -- let
alone design for -- the demands of a 21st century dot-com application. To work
in the Web browser world, the 3270 application needs to be redesigned for what
Rhyne refers to as ''Internet loads.''
''One of the principal performance factors is what I call the 24-by-80
interface bias,'' he explained. ''You may run a query and that query may return a
fair amount of information. But you can only serve up 24 rows of 80 characters
each because the application was originally written to drive a 3270 screen. And
a Web browser can show a lot more information than that. So typically, the first
thing people do is rewrite this application to return the entire query directly,
maybe in 32K chunks, maybe in 100K chunks. It's that kind of application
modification that typically is the first step customers will take in
The redesign of 3270 applications frequently requires older programmers --
who are maintaining COBAL and PL/1 applications -- to collaborate with younger
Java specialists working on Web services, Rhyne said.
Recognizing the problem and the opportunity, IBM is providing tools to link
the Web services of 2003 to the applications of 1973.
Rhyne asserts that the 3270 issue is tackled ''in the WebSphere Studio
Enterprise Developer product, which is specifically aimed at enterprise
developers, including those folks with COBOL and PL/1 application development
responsibilities. They can re-craft these applications to create the new
connectors they need to bridge that gap between that world and the J2EE world,''
For more information, go to http://www-3.ibm.com/software/info1/websphere/.
Rich Seeley is Web Editor for Campus Technology.