A couple of things:
Oracle bought RDB and got great cluster technology to build
their Oracle-RAC product-
I still have customers using Alpha servers and VMS- most
TRU64 unix customers have disapeared-they will migrate to Itanium
have only seen a couple of PDP11- runing RSX11m or RT11 for shop control machines-
I still have some customers running Vaxes-purchased about
1988 !! they think it is funny that the app will never be upgraded or replaced.-
I just recieved an order for a used VMS Alphaserver to replaced an older server from 1996! ( they were nervous about getting spare parts)
DOW rolled out a whole bunch of Vaxen and are upgrading to the IA64 platforms for their production systems after they did a 5 year study on the cost of ownership, after they had all moved over to MS systems. The cost of ownership on VMS was 40-60 less for them on VMS. I make an extra effort to support those folks.