Availability considerations
Syslogd availability is important to the logging of both local and remote messages. The following configuration considerations can help improve the availability of the z/OS® syslogd remote logging services:
- Ensure that there is a process in place to restart a z/OS syslogd after a failure that results in the termination of syslogd. This can be accomplished by placing syslogd in the AUTOLOG list in the TCP/IP profile. This enables TCP/IP to initially start the syslogd instance as a started task, and also enables TCP/IP to monitor whether syslogd has a socket bound to the syslogd port used for remote message receipt (UDP port 514). This approach works well for single-stack INET configurations. If multiple TCP/IP stacks are deployed on a single system (that is, a CINET configuration), you should not use the AUTOLOG list. Alternatively, an installation can use any available automated operations software package to automate the start and restart of syslogd. For more information about the AUTOLOG statement, see z/OS Communications Server: IP Configuration Reference.
- On MVS™ systems that are not part of a sysplex and that have TCP/IP stacks with multiple network interfaces, using a static VIPA address can provide for better availability characteristics should a specific network interface or network experience an outage. This involves configuring a static VIPA in the TCP/IP profile or reusing an existing one. No special configuration of the local syslogd is needed. However, you should configure the remote syslogd instances to use the static VIPA address as the destination address when forwarding messages. This can typically be accomplished by either specifying the static VIPA as the destination address, or specifying a host name that maps to the static VIPA in the remote syslogd configuration.
- When the recipient syslogd instance is running in a sysplex environment, additional availability features are available that should be explored. For example, you can use a multiple application-instance dynamic VIPA (DVIPA) to represent the syslogd instance on a given system, and the remote syslogd instances are configured to use that DVIPA address as the destination IP address for the messages they forward. In this configuration, if a failure to the MVS system or TCP/IP stack on which the syslogd instance is running occurs, the DVIPA is automatically moved to a predefined backup system that is currently active. This enables the syslogd instance on that backup system to begin processing these remote messages in a transparent manner. In this configuration, using the MVS operations log (OPERLOG) as the destination provides additional benefits, because the operations log is implemented as a coupling facility log stream that any system in the sysplex can access. For additional information related to static and dynamic VIPAs, see Virtual IP Addressing.