There are too many systems in banks that aren't documented and no one bothered to keep the source code. There are databases that contain ascii, ebcdic and binary packed decimal. I replaced a program once that I thought I knew what it was doing only to discover that because it was looking at every customers data it was creating a file that had a 1 bit flag for every customer that met some unspecified criteria. 6 weeks later another department complained that they were getting the exact same report everyday. Lesson learned. If you don't have the source code don't mess with the programs and even if you do you would have to reverse engineer every possible thing the program did. COBOL will be around until the last bank fails.