Some environment variables are read by UniBasic only during startup and so any changes will have no affect on the current UniBasic process. The following environment variables cannot be set nor modified from UniBasic for the running UniBasic process:
ALTCALL, BCDVARS, FORNEXTNEST, GOSUBNEST, INPUTSIZE, ISAMBUFS, ISAMSECT, ISAMFILES, LUST, NUMLINES, PORT, PORTS, PROGSIZE, TERM, VARSIZE and WINDOWS.