I came across an issue where two ESX servers that had been running for approximately 8-9 months without a reboot suddenly showed offline status in VCenter. Looking at the events in vCenter, it showed that the ramdisk 'TMP' was full and could not write to file /tmp/.SapInfoSysSwap.lock.LOCK.#####.
I got consoled into the ESX hosts and saw that there was a log file that had consumed most of the space at /tmp/mili2d.log. From what I read, this file would have been removed upon rebooting the ESX Host, but that was not something I wanted to have to do if I could help it.
I reviewed the log file and determined there to be nothing of significance inside, but it had been filling up for months until reaching the limit on both hosts. I thought I would just remove the file and reclaim the storage space, but that didn't reclaim the space.
You can check the space allocation with command "vdf -h". Here you can see the space left on the RAM Disk.
In order to get the ESX host to rescan the RAM Disk, restart the management services with "services.sh restart". After I did this, the space allocation showed available, and the ESX hosts showed online again within vCenter without having to reboot the servers.