On vSphere Client, "Host hardware system board status" alert appears in ESXi host summary.
You see "System Board x SEL_FULLNESS" (x=0, 1,...)" alert by navigating the hardware health of the Host.
You can find hardware health for the ESXi host by following the below steps.
VMware vSphere ESXi 8.x
VMware vSphere ESXi 7.x
This alert indicates that the BMC's saved IPMI (Intelligent Platform Management Interface) log count in BMC (Baseboard Management Controller) has exceeded its predefined threshold on the system board
You may need to clear out the IPMI event logs in your BMC. Because the steps change depending on which server or hardware you are using, we recommend checking with your hardware manufacturer for guidance.