ORA-01031 insufficient privs error : connect sys/password@SID as sysdba doesn't work

sqlplus '/as sysdba'

ERROR:
ORA-01031: insufficient privileges

sqlplus /nolog

SQL> connect sys/passwd as sysdba
ERROR:
ORA-01031: insufficient privileges

The ORA-01031: “insufficient privileges” error occurs when you attempt to execute a program or function for which you have not been granted the appropriate privileges.   For the DBA, the ORA-01031 can happen if the target OS executables do not have read and execute permissions (e.g. (770) in UNIX/Linux), and ensure that the oracle user is a member of the dba group (e.g. /etc/group). 

There is similar permission in the Windows registry.

The below steps will help you resolve this issue.

Resolution Steps: for DBAs

- Make sure that the user is part of DBA group

-change sys password using orapwd

orapwd file=$ORACLE_HOME/dbs/orapwDB1 password=system entries=10

or

orapwd file ORACLE_HOME\dbs\orapwDB1 password=system entries=10

-remote_login_passwordfile exclusive

-         If not working, just restart the database and listener.

-         If it is non system/sys user, ask DBA to grant necessary privileges to connect the database.

Windows specific steps

1. Checked that the Task Scheduler service in the Services control
panel of NT is logging on as a user that is part of the ORA_DBA or
ORA_<SID>_DBA group.

2. REMOTE_LOGIN_PASSWORDFILE is set to SHARED or EXCLUSIVE in
the Oracle parameter file (init.ora).

3. Verify that SQLNET.AUTHENTICATION_SERVICES=NTS is set in the
SQLNET.ORA file


If you're using Windows NT, do:

1) Open up "My Computer"
2) Open up "Scheduled Tasks"
3) On the toolbar, click on "Advanced"
4) Click on "AT Service Account"
5) Choose "This Account:"
6) Specify an NT account name and password that is part of the ORA_DBA or ORA_<SID>_DBA group


If you're using Windows 2000, do:

1) Open "Control Panel"
2) Click on "Scheduled Tasks"
3) On the toolbar, click on "Advanced"
4) Click on "AT Service Account"
5) Choose "This Account:"
6) Specify a Windows 2000 account name and password that is part of the ORA_DBA or ORA_<SID>_DBA group

SQL*Plus: Release 9.2.0.3.0 - Production on Thu Nov 20 10:44:43 2011
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.3.0 - 64bit Production
With the Partitioning, OLAP and Oracle Data Mining options
JServer Release 9.2.0.3.0 - Production

SQL> connect sys/password1 as sysdba
Connected.