Library /sys$common/syshlp/ncphelp.hlb SET, CIRCUIT, INACTIVE THRESHOLD number  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Applies to DDCMP CONTROL circuits.  It specifies the number of
 times to poll the active tributary before changing that
 tributary's polling state to inactive because of no data
 response.  Number must be a decimal integer in the range 0
 to 255. The default number is 8.