I recently added a group of tags (roughly a 100) to my PI database a month. Everything was working fine up until 5 days ago. Every night around the same time this select group of tags start collecting "Out of Serv" as its value. In order to resolve this issue, I have to restart the PI-ICU on the server where the interface for these tags reside on. I have over 3200 tags associated with this interface and only this group of tags seem to have issues. One thing I noticed in the PIPC.log file is that I'm getting the message below around the time I start having issues. With that being said, I would think that if I was indeed having interface issues then it should effect all tags associated with the interface in question.
OPCIntDWX.exe>PI-API> pinetread> recv: piserver:5450  An existing connection was forcibly closed by the remote host.