The z/OS Network File System server records diagnostic information (messages) in the z/OS NFS server log data sets specified in the NFSLOG1 and NFSLOG2 DD statements of the server's startup procedure.

The z/OS NFS server also records messages and debug trace information in a z/OS component trace buffer if specified. Using a component trace buffer can provide performance improvements compared to the log data sets. For details, see Using z/OS component tracing.

NFSLOG1 is associated with the primary log, while NFSLOG2 is associated with the secondary log. When the server is started, both the primary and secondary logs are opened for writing. As a result of this processing, the existing contents of both logs are destroyed. To preserve the contents of the logs from the previous server instance, the logs must be copied prior to the start of the server. If either the NFSLOG1 or NFSLOG2 DDNAME is not specified in the NFS server startup procedure or if an error occurs when attempting to open the data sets, NFS Server initialization will fail.

The primary log is used first. When the primary log is full, the logging is automatically switched or toggled to the secondary log and a console message is displayed. The last log buffer is lost when the switch takes place.When the secondary log is also full, the logging is switched back to the primary log and the original primary log content is cleared before writing to the log is started.

The number of log records depends on the log level setting and the number of transactions that the server handles. Adjust the space allocation of your z/OS NFS server log data sets according to your installation experience to avoid frequent log switching.