Troubleshooting OCI and Pro*C/C++ Applications

On Windows, if NLS_LANG is not set in the environment, the NLS_LANG setting is taken from the registry, HKEY_LOCAL_MACHINE\Software\ORACLE\NLS_LANG. If NLS_LANG is set to an invalid value or if NLS_LANG indicates an unsupported character set, either an OCI connection failed error or an ORA-12705 error is thrown.

See Globalization Support in TimesTen OCI in the Oracle TimesTen In-Memory Database C Developer's Guide for more information on NLS_LANG.