Is it really better if we replace x million lines of COBOL with x million lines of java or c++? What is the financial language of the future that is easy to write and reduces errors?
1. it would run on a modern environment instead of a weird mainframe OS using a weird database
2. it would use modern coding conventions such as local variables and control structures instead of goto
3. it wouldn't be x million lines after you remove all the dead and duplicate code. These are codebases have been developed for 3 decades with the principle "we don't know how any of this old shit works, don't touch anything you don't need to"
But yes, you would also get a lot of advantages from porting everything to a modern programming language with good tooling.
We were working, around 2000, on partially porting a Cobol+Fortran insurance system (which was an 'integration' of systems acquired by acquisition over the years) to Java (yes, EJBs..... ..... ..... the sins of my youth...). The work was mostly 20 people working for months on creating all the encoded rules into spreadsheets and, in a much shorter time, us translating those to Java. This particular piece was done because the company wanted to webify that part of the system. I am not sure if the modern versions of 'software mainframes' or modern hardware mainframes would be fast enough to handle web with the old code running?
http://www.fujitsu.com/global/products/software/developer-to...
The banking processes and environment are not though.