Re:The IBM mainframe: How it runs and why it survives
by tracker1 on Tuesday July 25, 2023 @11:31AM
(#36863780)
Have you ever migrated a decades old application off of a mainframe?
Most of these kinds of systems have decades of codified knowledge that applies the legal requirements of many disparate jurisdictions in these systems. Laws vary from city to city, county to county and state to state, and that's only for the US. Some of these systems implement code that applies legal requirements for dozens of nations.
In general, you're going to have to spend at least a year just to document the existing system. Another six months to a year generating test cases and scripts for validation. And that's before even starting to build the new system. And that is ALL optimistic, assuming everything goes right.
I had to once write a relatively simple application for "vacation bidding" where in employees will get a position to request certain weeks off during the year. This was a legal requirement and happened to involve the company, two other companies that had been merged in and three unions. Each with different rules regarding how seniority is calculated. The contractual specifics were over two thousand pages long. That's just one very small piece of software in one of these very large companies. It took the better part of a year to implement. Now imagine taking that a couple decades later after it's evolved and migrating to an entirely new platform and paradigm. Now imagine the cost to do that.
Most of these kinds of systems have decades of codified knowledge that applies the legal requirements of many disparate jurisdictions in these systems. Laws vary from city to city, county to county and state to state, and that's only for the US. Some of these systems implement code that applies legal requirements for dozens of nations.
In general, you're going to have to spend at least a year just to document the existing system. Another six months to a year generating test cases and scripts for validation. And that's before even starting to build the new system. And that is ALL optimistic, assuming everything goes right.
I had to once write a relatively simple application for "vacation bidding" where in employees will get a position to request certain weeks off during the year. This was a legal requirement and happened to involve the company, two other companies that had been merged in and three unions. Each with different rules regarding how seniority is calculated. The contractual specifics were over two thousand pages long. That's just one very small piece of software in one of these very large companies. It took the better part of a year to implement. Now imagine taking that a couple decades later after it's evolved and migrating to an entirely new platform and paradigm. Now imagine the cost to do that.