Windows: Local or Bequeath Connections As Sysdba Fail With TNS-12557 or TNS-12560

(Doc ID 397231.1)

Last updated on JULY 01, 2016

Applies to:

Oracle Database - Enterprise Edition - Version to [Release 8.1.7 to 11.2]
Oracle Net Services - Version to [Release 8.1.7 to 11.2]
Microsoft Windows x64 (64-bit)
Microsoft Windows (32-bit)


With a single installation of an older version Oracle database it was possible to use SQL*Plus with "connect / as sysdba" to make a local connection to the database. Since installing a higher version of product into a separate Oracle home, this method has started to fail with the following error: 

D:\>set ORACLE_SID=mysid

D:\>sqlplus /nolog

SQL*Plus: Release - Production on Mon Oct 16 08:44:52 2006
Copyright (c) 1982, 2005, Oracle. All rights reserved.

SQL> connect sys/**** as sysdba
ORA-12557: TNS:protocol adapter not loadable

You might also see the following error ORA-12560:

D:\oracle\product\\database>set ORACLE_SID=mysid
SQL*Plus: Release - Production on Fri Jul 18 04:48:54 2008
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Enter user-name: / as sysdba
ORA-12560: TNS:protocol adapter error




This problem can arise when another installation of Oracle products into a separate ORACLE_HOME would cause this problem as it has changed the environment.


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