and it must be related to Windows Environment or Oracle Home PATH because sqlplus command works smoothly when I execute it inside ORACLE_HOME\bin.
RUN: SYSDM.CPL to open Windows System Properties
Click on Advanced Tab > Environment Variables…
Click the Path variable under System Variable, then click Edit…
change the order between Oracle Client Home and Oracle DB Home:
From: D:\oracle\product\10.2.0\client_1\bin;D:\oracle\product\10.2.0\db_1\bin;
To: D:\oracle\product\10.2.0\db_1\bin;D:\oracle\product\10.2.0\client_1\bin;
in other words, put the Oracle DB Home in front of the other path.
Or i Don’t love this way , Since its not actual solution but its solve problem sometimes :
1-Remove ORACLE_HOME From environment Variable .
2- Restart PC
Done
Osama mustafa