Issue connection an ASP.Net site with two Oracle database on same server

I've taken over a ASP.Net site using an Oracle back-end, I can get it to connect to the database on our development PCs but on the live server, I'm having an issue as follow and wonder if anyone could help as not an Oracle expert and the Oracle server was setup many years ago...

There is two databases on the same oracle server serving a similar purposes with similar sites but for different clients. For this, I will call them DB1 and DB2. DB2 database was added recently, up until now, only DB1 was in use.

The existing site has been working fine up to now and is still working and has the following connection string in the web.config file: (I replaced the DNS, UID and PASSWORD with * but the key element here is that DBQ is configured as "ORACLE", yet the name of the database IS NOT ORACLE but DB1, however, connection works.

sessionState mode="InProc" stateConnectionString="tcpip=127.0.0.1:42424" sqlConnectionString="data source=127.0.0.1;Trusted_Connection=yes" cookieless="false" timeout="20"

appSettings
add key="OracleConnection" value="DSN=***;UID=***;PWD=*****;DBQ=ORACLE;"
add key="ChartImageHandler" value="storage=file;timeout=20;dir=c:\tempimages;"
appSettings

Having added the 2nd database for client 2, I now wish to run the same site but from a different folder. The problem is if I run the site with the same connection as below, it obviously connects to the client 1 database and not client 2. As we do on our development machines, changing the DBQ to the correct database name is the way to point the site to the correct database but in this case, it isn't, if I use the actual names of the database (DB1 or DB2, neither connects at all), it seems only the string ORACLE works but obviously it point to the DB1 database only.

So I would like to know if there is some kind of "alias" or mapping setting on Oracle that means that the "ORACLE" connection string default or point to the first or default database? and if yes, how can it be turned off so I can use just the database names as we do on our development machines which works fine. Or could there be another reasons for this oddity?

Thanks in advance