The following are all things that an application might do that, without the use of the Mainframe Call Generator, would prevent it from being used:
- Communicate with a third-party product on the mainframe.
- Use MVS/390 control blocks that are not supported.
- Communicate with database systems that are not available on the PC, such as DATACOM.
- Call subprograms written in an MVS/390 programming language such as C, C++ and Java, for which there is no PC version because of the required EBCDIC support.