During work today I tweaked the online tunable called filecache_max on an HP-UX 11.31 box. From 1 to 5%. Went fine. I tested what I needed to test and then decided to lower the value again. So I ran kctune filecache_max=2% and then nothing.
Everything(!) stopped working. Well, the system could be pinged, but the other cluster node started to complain about its sister disapperaing. I littlerally got cold hands. This was supposed to be an online operation. I waited for 4 very very long minutes (being a computer professional have learned me to wait for stuff to finish).
After 4 minutes the system was back. Running as nothing had happened. Everything littlerally just froze up trying to reduce the filecache. I learnt it the hard way. Hope this post will prevent you from getting into the same kind of troubles.