z/OS NFS with Sun NFS V2 protocol provides two processing attributes that only apply to z/OS UNIX processing. The sync attribute specifies that z/OS UNIX write requests should be committed to nonvolatile media (for instance, DASD) when received by the server. Some performance improvement can be obtained with the alternative async processing attribute. This type of processing causes z/OS UNIX write requests to be cached at a level within the z/OS UNIX architecture prior to the physical I/O. For more information about z/OS UNIX tuning, see Ordering out-of-sequence data and Subtasking.

The async and sync attributes specified in the control file are ignored when z/OS NFS server is communicating with Sun NFS V3 and V4 protocols. The processing attribute is determined in the client application implementation. Asynchronous write is also recommended for faster throughput.