以下适用于Windows 2003：
不少人在做ASP.NET+Oracle开发的时候都会碰到连接问题，提示“Unable to load DLL (oci.dll)”，但这个文件在系统中是存在的，很多人为此焦头烂额，我看到很多的帖子都是求助这个问题的。其实并非所有的人都会碰到这个问题，只在于用硬盘分区格式为NTFS的用户，既然oci.dll文件时存在的，那么访问不到就自然是权限的问题了，解决方法如下：
例如你的Oracle是装在C盘中，目录为“C:/Oracle/Ora92/”，那么需要针对Ora92这个文件夹设置权限就可以了，“属性 -> 安全 -> 添加 -> ASPNET”，该用户权限都是默认的即可。
http://blog.csdn.net/heyixiang/article/details/449306
以下适用于Windows 2003/XP:
Solution Description
——————–
Oracle 9.2 Client software requires that you give the Authenticated User privilege to the Oracle Home by following these steps:
1. Log on to Windows as a user with Administrator privileges.
2. Launch Windows Explorer from the Start Menu and navigate to the ORACLE_HOME folder. This is typically the “Ora92″ folder under the “Oracle” folder (i.e. D:\Oracle\Ora92).
- the "Ora92" folder under the "Oracle" folder (i.e. D:\Oracle\Ora92) in Oracle9iR2
or
- the "Client_1" folder under the "Oracle\product\10.1.0" folder (i.e. D:\Oracle\product\10.1.0\Client_1) in Oracle10gR1
or
- the "Db_1" folder under the "Oracle\product\10.1.0" folder (i.e. D:\Oracle\product\10.1.0\Db_1) in Oracle10gR1
3. Right-click on the ORACLE_HOME folder and choose the “Properties” option from the drop down list. A “Properties” window should appear.
4. Click on the “Security” tab of the “Properties” window.
NOTE: If you are running Windows XP and do not have a "Security" tab, please do the following:
(a) Open "Folder Options" in your Control Panel.
(b) Choose the "View" tab.
(c) Under "Advanced Settings" uncheck the option "Use simple file sharing (Recommended)".
The "Security" tab should now be available.
5. Click on “Authenticated Users” item in the “Name” list (on Windows XP the “Name” list is called “Group or user names”).
6. Uncheck the “Read and Execute” box in the “Permissions” list under the “Allow” column (on Windows XP the “Permissions” list is called “Permissions for Authenticated Users”).
7. Re-check the “Read and Execute” box under the “Allow” column (this is the box you just unchecked).
8. Click the “Advanced” button and in the “Permission Entries” list make sure you see the “Authenticated Users” listed there with:
Permission = Read & Execute
Apply To = This folder, subfolders and files
If this is NOT the case, edit that line and make sure the “Apply onto” drop-down box is set to “This folder, subfolders and files”. This should already be set properly but it is important that you verify this.
9. 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.
10. Reboot your computer to assure that these changes have taken effect.
Re-execute the application and it should now work.