Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.112.0P1 - Page 352

System Log Event messages provide system administrators diagnostics and auditing information. Dell Networking OS sends event messages to the internal buffer, all terminal lines, the console, and optionally to a syslog server. For more information about event messages and configurable options, refer to Management. Hot-Lock Behavior Dell Networking OS hot-lock features allow you to append and delete their corresponding content addressable memory (CAM) entries dynamically without disrupting traffic. Existing entries are simply shuffled to accommodate new entries. Hot-Lock IP ACLs allows you to append rules to and delete rules from an access control list (ACL) that is already written to CAM. This behavior is enabled by default and is available for both standard and extended ACLs on ingress and egress. For information about configuring ACLs, refer to Access Control Lists (ACLs). Process Restartability Process restartability is an extension to the Dell Networking OS high availability system component that enables application processes and system protocol tasks to be restarted. This extension increases system reliability and uptime by attempting to restart the crashed process on primary RPM before executing the failover procedure as a last resort. Currently, if a software exception occurs, Dell Networking OS executes a failover procedure. In a single-RPM system, the system generates a coredump and reboots; in a dual-RPM system, the system generates a coredump and fails over to the standby RPM. With a system reload, the system must read and apply the entire startup-config file, which might take some time if the startup-config is large. Restarting a process saves time because only a portion of the configuration related to the crashed process is read and reapplied. For a dual-RPMs system, restarting a process also precludes launching the failover process on the primary and standby RPMs. Recovery is attempted first locally on the primary RPM, which involves less CPU overhead, increasing the systems availability for other activities. However, in both single and dual-RPM systems, even when you configure process restart, the coredump portion of failover is still executed. The processes that you can restart fall under three categories: • Interface-related processes - TACACS+, RADIUS, CLI, and SSH, and so on. • Protocol tasks - OSPF, RIP, and ACL, and so on. Process restart is not currently available for protocol tasks; the failover procedure is executed immediately after software exception. • Line card processes - IPC, Event Log Agent, Line Card Manager, and so on. Process restart is not currently available for line card processes; the failover procedure is executed immediately after software exception. Enabling Process Restartability The restart time varies by process. In general, interface-related processes are hitless and can be restarted in seconds; if a restart is successful, traffic is not interrupted. Protocol tasks and line card processes are not hitless and take longer to restart. You can select which process may attempt to restart and the number of consecutive restart attempts before failover, but by default, every process fails over. • Enable process restartability for a process or task. CONFIGURATION mode process restartable [process] [try number] [timestamp hours] • Display the processes and tasks configured for restart. 352 High Availability (HA)