In order for the dataserver to select the dll you do not need to modify the PATH as previously suggested but by setting environment variable "ORADLLPATHNAME"..
For example, if oci.dll is available in c:\oracle\oracle11rg-32\bin\ directory, then %ORADLLPATHNAME% should be
Also make sure that the ORACLE_HOME environment variable matches Environment property of the unified Oracle DataServer broker.
Modify the value of the ORACLE_HOME environment variable of the unified Oracle DataServer broker from the Progress Explorer tool, and point it to the correct Oracle directory.
This value can be found in the registry: