Mixing OLTP with DSS

[Rick Stephenson]

Am I looking for trouble by mixing an OLTP type database with a DSS type database?   I currently have a relatively small database that is used for quick lookup type actions.  The company wants to add a much bigger and constantly growing application for historical reporting on the same machine.  Should I create another instance or keep it in the same instance?   Keeping it in the same instance would seem to defeat having anything cached seeing that the large reports will flush out the cache each and every time.   I am running Oracle 8.1.7, on Solaris 2.8.   Any suggestions would be helpful.   Thanks,   Rick Stephenson