Granny's Programming Pearls
"inside of every large program is a small program struggling to get out"
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Part II - Question on legacy system

 
Sridhar Raman
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Hi folks,
I am looking at part II after having passed passing part I a year and a half ago!
I got a little confused reading the requirements on what needs to be done with the legacy system. I have two questions.
1. I don't understand quite well how a terminal based legacy system works. Are the terminals thick clients that access the data from the IMS database? Or, are the terminal dumb terminals that go through one huge (kind-of-an) application server that does all the talking with the backend IMS database?
2. The requirements mentions about replacing the terminal based interface with GUI and the legacy database with an RDBMS. Are we talking of scraping off the legacy and rewriting it anew with J2EE architecture here? If the terminals are thick clients, then in effect we are scraping off the old system and replacing it with a new one.
If the terminals are dumb-terminals, then we will still have the legacy application to deal with and in this case it would be a matter of designing legacy interfaces and changing the GUI.
The main thing is my total ignornace of how legacy systems operate. If anyone can throw some light on this and respond my two questions that I have posed, that will be greatly appreciated.
thanks a lot in advance
Sridhar
 
Rufus BugleWeed
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Are we talking of scraping off the legacy and rewriting it anew with J2EE architecture here?

yes - but not the frequent flyer system
 
Sridhar Raman
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Thanks, Rufus.
This means that the old system will not exist any more, once the web based system goes live. When the requirements mention about making the user interface for the travel agents more appealing by replacing the 3270 terminals, they are actually talking about replacing the whole legacy system. Why couldn't they be more clear about this!
I wonder if anyone tried to support the existing legacy system, in their architecture...

Sridhar-
 
It is sorta covered in the JavaRanch Style Guide.
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