It is generally unwise to separate the ArcSDE application server from the database to
which it is tightly coupled, unless you also intend to create a dedicated point-to-point
network between the ArcSDE server and the database (crossover cable, backplane to
backplane, gigabit speed). This was especially true way back when 9.0 was released.
The only real reason to configure a distributed install is to handle a clustered database
configuration, in which case all connections should be Direct Donnect, and the application
server component isn't really necessary.
I urge you to learn a bit more about ArcSDE, and a lot more about GIS. Once you start
using a modern database, you'll see that the division between roles of DBA and GIS
database administrator has become moot (all modern databases have native spatial
datatypes).
- V