The z/OS NFS server has no control over available space for a data set on disk and cannot automatically extend to the available space on the disk. During writing to disk from the z/OS server, x37 Abends can occur more readily when data sets are created with small SPACE primary and secondary allocation units. For the z/OS server to avoid possible x37 Abends, data sets should be allocated with primary and secondary SPACE allocation units to fit the largest byte data stream from an NFS client. Due to asynchronous write between the z/OS NFS server and the NFS client, the NFS client may not get a no-space-on-disk error as a result of an x37 Abend on the z/OS server side if the z/OS server has to flush cached data and close/deallocate a data set at a time other than a write or commit request, such as after writetimeout expiration. For small data set allocations, there is a risk to lose data and get a no-space-on-disk error postponed due to z/OS server data caching.