Cause: There are two possible causes: Either an attempt was made to issue an ALTER SESSION statement with an invalid NLS parameter or value; or the NLS_LANG environment variable contains an invalid language, territory, or character set.
Action: Check the syntax of the ALTER SESSION command and the NLS parameter, correct the syntax and retry the statement, or specify correct values in the NLS_LANG environment variable.
Points to fix the issue:
1.simply set it with the below command
C:>set NLS_LANG=AMERICAN_AMERICA.WE8MSWIN1252. (if not fix,try with below procedure)
2.From start-->Run--->Type regedit--->HKEY_LOCAL_MACHINE-->SOFTWARE-->ORACLE-->HOME folder has a key
NLS_LANG as AMERICAN_AMERICA.WE8MSWIN1252.
change to AMERICAN_AMERICA.WE8ISO8859P15 may fix your connectivity issue. (Permanent fix, even if not fix try with below procedure)
3.Try this...
check if exist into windows registry (regedit) the oracle_home
Example
[HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE]
ORACLE_HOME=
if not create one.
and add the path into the windows variable PATH adding bin folder
example D:\Appls\Oracle\bin
Control Panel -> System -> Advanced Options -> Environment variables - > system variables -> path
4. Still not resolve
Just go regedit -->Oracle Home--and delete the NLS entries from there..You should be fine.
5. Final point if not solve with above points, uninstall and install Oracle client software.
