> You can’t just rewrite the whole thing.
Is it that bad? I guess I'm being crazy thinking I can do it single handedly in 5-10 years for a couple million.
For every 1 programmer working on a Cobol system who would and could rewrite it, there's another 3 who actively resist rewrites to keep their jobs and put bugs in the system to generate overtime-paying after-hours callouts. There's yet another 6 programmers who don't have the aptitude to program but who somehow managed to get into their job and are just productive enough to avoid being terminated. And perhaps they bring one of their kids to work for the day every now and then.
You don't get to do a Cobol rewrite single-handedly when there's 9 others on the team working against it happening.
But that also means the major roadblocks are sociopolitical and not technical (not saying technical challenge is not there, just that it's not the biggest issue).
I'm not saying I'll do things the conventional way. Once you give up the conventional way, it becomes a different ball-game.
And it has complex, undocumented connections to north of a hundred other systems. Screwing up any one of which could have hugely impactful effects on the business (or not, who knows?). So you're going to be coordinating testing with 30-40 teams in diverse parts of the organisation (and externally).
And your couple of million won't pay for the redesign of all those feeds. Hopefully they won't take the testing costs out either or you'll be broke in 2 years.
See, the thing with extracting these old, large systems isn't really the language they're written in, or the hardware they run on. Though those are nasty, ugly problems. It's the coupling. What will almost always defeat you, unless you give the problem the respect it deserves (and often even then) is the coupling.
As for the couple million, that's for me :) But I guess if you factor in cost of supporting hardware/software/infrastructure, it's really past 5 million (maybe 10 million), just as an estimate.
To elaborate on my 'unconventional way', I'm talking about using all of:
- complete view of the source code,
- runtime behavior on the screen (even recorded with cameras, or even better, display debug hooks)
- runtime storage logging,
- runtime network logging,
- modern inference methods beyond parsing (semantic inference, logic programming, maybe even some statistical analysis).
- But most importantly, automation-first approach (no, we're not doing things by hand. 'The Machine TM' will do the work for us). E.g., I won't be reading the COBOL code line by line. The code, plus the runtime behavior, would be the input to the inference engine, the output would be 'explanations, documentation, etc'.
- and so on
It would be a very challenging project, hence the 5-10 year timeframe. But I'm not convinced it's intractable. And I'm not convinced the cost is in the billions.