Before you begin diagnostic procedures, verify that the suspected problem is not a result of failure caused by:

• z/OS® Communication Server's TCP/IP (Transmission Control Protocol/Internet Protocol)
• Broken clients (for example, sending incorrect file handles or ignoring the server’s error return code)
• The network (for example, packets not arriving at the server, clients not receiving replies, or a gateway going down)
• The result of user input error.

For failures caused by z/OS Communication Server's TCP/IP, see z/OS Communications Server: IP Diagnosis Guide to diagnose the problem.