Setting the UPSI Byte
If your program uses the user program switch indicator (UPSI) byte,
you can set it by using the UPSI operand of the CMS SET command. The
UPSI byte is initially binary zeros. To set it to ones, enter:
set upsi 11111111
To
reset it to zeros, enter:
set upsi off
Any value you set
remains in effect for the duration of your terminal session unless
you reload CMS (with the IPL command).