The acusavenv() routine records information about the state of the COBOL call stack and returns a pointer to a jmp_buf structure that can be passed to setjmp. You pass this routine an acujmp_buf structure, which carries the combined C and COBOL stack states.
jmp_buf * acusavenv(acujmp_buf *buffer)
refer to the entry on aculongjmp() for more information on using acusavenv(). See your C documentation for information on the setjmp and longjmp routines, as you need a working understanding of these routines to use acusavenv() and aculongjmp().
The acusavenv() function is intended for use with batch programs or programs written for a transaction processing system, allowing such systems to restart or recover from a failed service component. Therefore, they are not recommended for programs that use the ACUCOBOL-GT graphical user interface, which are typically event-driven and multithreaded.