Because businesses depend heavily on the availability of data processing systems, problems in the network must be addressed quickly. Symptoms of a network problem might include error messages, unusual system behavior, slow response time, or no system response.

The network administrator should first determine the general cause of the problem by reading error messages, checking for system memory dumps, checking to see if software or hardware has changed, and reading the system log. After determining the general cause of the problem, the network administrator should use the tools and diagnostic aids at hand to determine the specific cause of the problem. Lastly, tuning tasks should be carried out to ensure good network performance.

z/OS has diagnostic aids that the network administrator can use: abend dumps, stand-alone dumps, and supervisor call (SVC) dumps, which the Interactive Problem Control System can format for easier reading. Additionally, VTAM has specific aids, such as First Failure Support Technology, CSDUMPs, network traces, sense codes, VTAM traces, and commands that display the state of VTAM components and resources. TCP/IP has component traces and diagnostic commands (such as the NETSTAT command) that help determine problems in the IP network. Communications Storage Manager (CSM) problems generally manifest themselves as central storage problems. The network administrator can display CSM's use of storage, activate CSM VTAM traces, and dump CSM storage for analysis.