On VAX systems, SCSBUFFCNT is the number of buffer descriptors
    configured for all systems communication architecture (SCA). If
    an SCA device is not configured on your system, this parameter is
    ignored. Generally speaking, each data transfer needs a buffer
    descriptor and thus the number of buffer descriptors can be
    a limit on the number of possible simultaneous I/Os. Various
    performance monitors report when a system is out of buffer
    descriptors for a given workload which is an indication that
    a larger value for SCSBUFFCNT is worth considering. Note that
    AUTOGEN provides feedback for this parameter on VAX systems only.

    On Alpha and Integrity servers, the system communication services
    (SCS) buffers are allocated as needed, and SCSBUFFCNT is reserved
    for VSI use only.

    SCSBUFFCNT has the AUTOGEN, FEEDBACK, and GEN attributes.