Sahil,

If you just want to use Oracle in your own modules there is a simple solution. Look at Entity Spaces http://www.entityspaces.net/portal/.

I use ES for my modules and regularly access a database other than the DNN SQL db. Apart from giving you the ability to access Oracle it will also save you lots of time because it generates all your db access code and Stored Procedures.

As an example - this is my function to read my db:

Public Function CustomGetEventsByRange(ByVal ModID As Integer, _
                                               ByVal StartDate As DateTime, _
                                               ByVal EndDate As DateTime, _
                                               ByVal Category As String) As Boolean

            Dim esParms As esParameters = New esParameters()
            With esParms
                .Add("Modules", ModID)
                .Add("StartDate", StartDate)
                .Add("EndDate", EndDate)
                .Add("Category", Category)
            End With

            Return MyBase.Load(esQueryType.StoredProcedure, "dws_SimpleEventsGetByRange", esParms)

        End Function

In this case I am calling my own custom SP.

Go look at it I expect you will be impressed.

FYI: my only connection with Entity Spaces is that I am a very happy customer

In your oracledataprovider class that you've created for your module, you would override the section that reads the data connection string and point it to some other section from web.config. This would allow you to specify in web.config a separate connection string for your oracle database.

In your stored procedure calls to the db, you would also have to use the oracle version of the datareader classes, etc so as to pull the right data from Oracle. If you pass in to this the new connection string for Oracle, this would allow you to connect to Oracle and retrieve whatever data you need.
The one thing that might be tricky to do is that DNN uses reflection to determine which dataprovider to use (ie which dataprovider.dll to use).. In your case, since your site itself is in SQL Server, I'm pretty sure it would try and load your SQL Server version of the dataprovider class - what you could do is fool the system to think that it's using the SQL Server version by naming your oracledataprovider to be sqldataprovider.

Sanjay