VMS Help Sys Parameters, CLUSTER_CREDITS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    CLUSTER_CREDITS specifies the number of per-connection buffers a
    node allocates to receiving VMS$VAXcluster communications.

    If the SHOW CLUSTER command displays a high number of credit
    waits for the VMS$VAXcluster connection, you might consider
    increasing the value of CLUSTER_CREDITS on the other node.
    However, in large cluster configurations, setting this value
    unnecessarily high consumes a large quantity of nonpaged pool.
    Each receive buffer is at least SCSMAXMSG bytes in size but might
    be substantially larger depending on the underlying transport.

    It is not required for all nodes in the cluster to have the
    same value for CLUSTER_CREDITS. For small or memory-constrained
    systems, the default value of CLUSTER_CREDITS should be adequate.