Oracle and the Oracle client is irritating to me to say the least. I support a few apps that speak to an Oracle 9i database and have not had a lot of trouble with them that checking the databases does not seem to solve, I consider myself lucky.
Twice though in the last couple of weeks I have run into apps on Citrix that just did not want to play well with an Oci.dll could not be loaded error. I looked through the app documentation and of course there is nothing but on looking further the first time I found that Authenticated users needed to have modify access to the ora92 folder.
Today the problem that I had dealt with the Oracle instant client that was bundled with the same application, which will remain nameless, but after testing it outside of Citrix – directly from the server there were no problems, after running from Citrix i found that the regular users would have a problem logging in with the same Oci.dll error. I checked permissions and found that the Oracle instant client folder did not have the aforementioned authenticated users rights but after fixing that I still could not run the application. Now I was kind of stuck and rn a filemon to see that low and behold the Citrix Client was not able to see the oracle client folder.
Now I had the fix. I added the Oracle instant clients folder to my path statement on the server and everyone was then able to work.