The bufhigh parameter specifies the maximum size in megabytes of allocated buffers for caching. z/OS NFS client uses this buffer area to cache file data, thereby satisfying requests efficiently.

When a client system is suffering high CPU utilization and low throughput, increase the bufhigh storage size. Increasing the bufhigh storage size by twice the default value (within available region) may improve system performance. Also, if the client system is processing mostly large files, it is good to increase the bufhigh storage size. Any changes to the bufhigh parameter require restarting z/OS UNIX.