/sys$common/syshlp/helplib.hlb SET, QUEUE, Qualifiers, /JOB_LIMIT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /JOB_LIMIT=n

    Indicates the number of batch jobs that can be executed
    concurrently from the queue. Specify a number in the range 1
    to 255.