Library /sys$common/syshlp/dbg$help.hlb DEBUG, Built in Symbols, %EXC SEVERITY  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Gives you the severity code of the current exception. This
    provides a way of qualifying exception breaks.

    Example:

    DBG> EVALUATE %EXC_SEVERITY
    "F"
    DBG> SET BREAK/EXCEPTION WHEN (%EXC_SEV = "F")