Sitecore & Oracle: 'Unhandled Execution Error' while connecting

I'm trying to run Sitecore 7 with Oracle and I'm stuck on an error. What I've done is

Let a DBA create all Oracle users / schemas / tables
Verified with Oracle SQL Developer that the databases are indeed created, accessible and containing tables
Make sure I'm using the correct web.config
Update my connection strings
Do all the other Sitecore setup that I would normally do (IIS site, VS solution, etc.)
Install Oracle Client tools (including all possible drivers for my 64-bit system)

I've tried two variations of connection strings:

user id=my_username;password=my_password;Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=my_host_name)(PORT=5151))(CONNECT_DATA=(SERVICE_NAME=my_service_name)))

and this one:

Data Source=my_username/my_password@//my_host_name:5151/my_service_name

Using the exact same information, I'm perfectly able to connect using the Oracle SQL Developer.

When I launch my Sitecore site, I get the following exception:

Unhandled Execution Error

Exception Details: Oracle.DataAccess.Client.OracleException:

[OracleException (0x80004005)]
Oracle.DataAccess.Client.OracleException.HandleErrorHelper(Int32 errCode, OracleConnection conn, IntPtr opsErrCtx, OpoSqlValCtx* pOpoSqlValCtx, Object src, String procedure, Boolean bCheck, Int32 isRecoverable) +1250
Oracle.DataAccess.Client.OracleException.HandleError(Int32 errCode, OracleConnection conn, IntPtr opsErrCtx, Object src) +91
Oracle.DataAccess.Client.OracleConnection.Open() +4698
....snipped...

Been struggling with this for a day now and would really appreciate some help. Anyone out there running Sitecore 7 on Oracle?

Solution

Make sure that you are using the Oracle client tools version 11g, other Oracle versions are not supported with Sitecore 7. See this link for a reference