I have installed 10.1 ArcGIS Desktop and ArcGIS Server on a 64 bit Windows Server 2008R2 virtual macine. I have an oracle database that I used with 10.0 and have successfully established a connection to it through ArcCatalog. When trying to register this database with ArcServer I get the error "The data item is inaccessible." So, looking through the documentation I realize that I haven't loaded the oracle client software. So I load the 64 bit client software. Knowing that I also am running Desktop I install the 32 bit client as well. I setup my environment variable Path to point to client_1(64bit) before (client_2) - as stated in the documentation. I then go back to Catalog to look at my database and the connection no longer works. If I take out the link to the 32 bit client in the Path environment variable, Catalog can connect to the database. I'm confused. I thought the 32 bit client was required if connecting to a database from Desktop. I would have thought that I wouldn't be able to connect to the database via Catalog without the 32 bit oracle client. I still cannot register the database in ArcServer. What am I missing/doing wrong?