ORA-12560: TNS:protocol adapter error
A generic protocol adapter error occurred
Check addresses used for proper protocol specification. Before reporting this error, look at the error stack and check for lower level transport errors. For further details, turn on tracing and re-execute the operation. Turn off tracing when the operation is complete.
ORA-12560 is defined as a generic protocol adapter exception and may have various reasons.
oracle@dba>sqlplus scott/tiger SQL*Plus: Release 126.96.36.199.0 Production on Wed Feb 20 18:44:04 2013 Copyright (c) 1982, 2011, Oracle. All rights reserved. ERROR: ORA-12560: TNS:protocol adapter error