System.Data.OracleClient requires Oracle client software version 8.1.7

I've run into this error dozens of times:

Cause

Security permissions were not properly set when the Oracle client was installed on Windows with NTFS. The result of this is that content of the ORACLE_HOME directory is not visible to Authenticated Users on the machine; this causes an error while the System.Data.OracleClient is communicating with the Oracle Connectivity software from ASP.NET using Authenticated User privileges.

Solution

To fix the problem you have to give the Authenticated Users group privilege to the Oracle Home directory.

• Log on to Windows as a user with Administrator privileges.
• Start Windows Explorer and navigate to the ORACLE_HOME folder.
• Choose properties on the ORACLE_HOME folder.
• Click the Security tab of the Properties window.
• Click on Authenticated Users item in the Name list.
• Un-check the Read and Execute box in the Permissions list under the Allow column.
• Re-check the Read and Execute box under the Allow column.
• Click the Advanced button and in the Permission Entries verify that Authenticated Users are listed with permission: Read & Execute, and Apply To: This folder, subfolders and files. If not, edit that line and make sure that Apply To drop-down box is set to This folder, subfolders and files. This should already be set properly but it is important that you verify it.
• Click the OK button until you close out all of the security properties windows. The cursor may present the hour glass for a few seconds as it applies the permissions you just changed to all subfolders and files.
• Reboot, to assure that the changes have taken effect.

Try your application again.

The author of this post (now deleted post) suggests checking your C:\Windows\System32 folder to make sure that the oci.dll exists there. Copying in the file from the Oracle home directory solved this problem for me.

Update 1: It is possible for different users to have different path. But its not the likely problem here. There is more chance that the user that the iwam user doesn't have permission to the oracle client directory.

Update 0: Its suppose to work. Check for environment variable ( That are needed to find the oracle client and tnsnames.ora ). Also, Maybe you have a 32/64 bit issues. Also, consider using the Oracle Data Provider for .NET ( search for odp.net)

Oracle Client version 11 cannot connect to 8i databases. You will need a client in version 10 at most.