(Alpha and I64 only.) The Get Previous Invocation Handle routine
    gets the previous invocation handle of any active procedure.

    A thread can obtain an invocation handle of the procedure context
    preceding that of a specified procedure context by using the
    following function format.

    Format

      LIB$GET_PREV_INVO_HANDLE   invo_handle

1 - Returns

    OpenVMS usage:invo_handle
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

    An invocation handle for the invocation context that is previous
    to that which was specified as the target.

2 - Argument

 invo_handle

    OpenVMS usage:invo_handle
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value

    An invocation handle that represents a target invocation context.