The z/OS Network File System client records diagnostic information (messages and debug trace information) in the z/OS NFS client log data sets specified in the NFSCMSG1 and NFSCMSG2 DD statements of the client's startup procedure.

NFSCMSG1 is associated with the primary log, while NFSCMSG2 is associated with the secondary log. When the client is started, 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 overwritten.

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