I came from a mainframe environment. I started with IBM 360 back in 1974. In 1980, I started with a system 38 (in COBOL). It was the best move I made except going to the AS400 (then iSeries). I have (for about a year) moved back to the main frame (I hated it). It would not allow temp work files (even create on the fly), the ability to put a program in production, having to ask system admin to be able to perform tasks assigned, and many more pains/headaches. Hate CICS and how the program functions around it. It is easier to just read a screen (like a database file) and stay within the program. The AS400 does many dynamic change (I understand that main frames allows some dynamic change) but the system 38 (back in 1980) allowed this. There is no comparison between the 2 in my mind and IBM created a great system but is losing money (because the AS400 is so simple to run). Ask any AS400 person and you would hear the same thing. The AS400 can run CICS (but who wants to) but can run AIX, JAVA, C, and many others along with RPG and COBOL. Hope you follow thru with the change to the AS400 world (after a short time, you will feel like the rest of us and will not want to go back to main frames). Good Luck!!