/sys$common/syshlp/helplib.hlb POSIX Threads, TIS routines, tis_cond_signal, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    When threads are present, this routine unblocks at least one
    thread that is waiting on the specified condition variable cond.
    When threads are not present, this routine has no effect.

    For more information about actions taken when threads are
    present, refer to the pthread_cond_signal() description.