Getting errors when connecting with an Oracle Instant Client (4310962)

The following errors may occur when using Oracle Instant Client. 

1. Can't initialize OCI. Error -1
2. The are no database connections to choose from the drop down list.
3. ORA-12705 Cannot access NLS data files or invalid environment specified.

How to configure my environment to use an Oracle Instant Client?

SOLUTION for error 1 (Can't initialize OCI. Error -1):

Locate file oraociicus10.dll on your PC and ensure that the folder  e.g. 'c:\oracle\instantclient' where this file resides is entered into your environment variable PATH statement as the first entry.  To check or edit the PATH statement:

1. Right click on the My Computer icon on the desktop and select Properties
2. Select the Advanced Tab
3. Click Environment Variables
4. Highlight Path under system variables | Edit | add e.g  'c:\oracle\instantclient'  to beginning of PATH statement | OK

On Vista or Windows 7 machines, right-click on SQL Nav icon and select "Run As Administrator" option.

SOLUTION for error 2 (The are no database connections to choose from the drop down list.):

Set up an environment variable TNS_ADMIN
1. Right click on the My Computer icon on the desktop and select Properties
2. Select the Advanced Tab
3. Click Environment Variables
4. Under the 'System Variables' window select New
5. Enter TNS_ADMIN for the 'Variable name' and the path to your tnsnames.ora file in the 'Variable value' boxes.
- For example if your tnsnames.ora resides in folder c:\oraclient10g\network\admin then this is the path you would specify as the 'Variable value.'
6. Click OK for changes to take effect
7. Reboot your PC

SOLUTION for Error 3 (ORA-12705 Cannot access NLS data files or invalid environment specified.):

Set up an environmental path variable NLS_LANG:
1. Right click on the My Computer icon on the desktop and select Properties
2. Select the Advanced Tab
3. Click Environment Variables
4. Under the 'System Variables' window select New
5. Enter NLS_LANG for the 'Variable name' and AMERICAN_AMERICA.WE8ISO8859P1 in the 'Variable value' boxes.
6. Click OK for changes to take effect
7. Reboot your PC

* Note: It is specified here to use AMERICAN_AMERICA.WE8ISO8859P1, but any NLS_LANG setting can be chosen.