Connecting “/ as sysdba” is successful if threaded_execution=false. It fails if threaded_execution=true. Lets verify this with an actual example:
1. Set the threaded_execution parameter value as true.
SQL> show parameter threaded_execution; NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ threaded_execution boolean FALSE
SQL> connect / as sysdba Connected. SQL> alter system set threaded_execution=true scope=spfile; System altered.
2. Shutdown and start the database instance for the changes to take effect.
SQL> shutdown immediate; Database closed. Database dismounted.
SQL> startup ORACLE instance started. Total System Global Area 413372416 bytes Fixed Size 2289016 bytes Variable Size 322962056 bytes Database Buffers 79691776 bytes Redo Buffers 8429568 bytes Database mounted. Database opened.
3. Verify if you can login into the database now.
SQL> connect / as sysdba ERROR: ORA-01017: invalid username/password; logon denied
SQL*Plus: Release 12.1.0.1.0 Production on Fri Mar 7 07:24:59 2014
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-01017: invalid username/password; logon denied
As you can see from the output, user can not login into the database. The only solution here is to use the username password for sys user.
$ sqlplus sys/XXXXXX as sysdba SQL*Plus: Release 12.1.0.1.0 Production on Fri Mar 7 07:25:05 2014 Copyright (c) 1982, 2013, Oracle. All rights reserved. Connected to: Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options
You can also verify the threaded_execution parameter value.
SQL> show parameter threaded_execution NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ threaded_execution boolean TRUE
4. Change the threaded_execution parameter value back to false to be able to login directly into the database without providing password.
SQL> alter system set threaded_execution=false scope=spfile; System altered.
5. Take a restart of database instance for the changes to take effect.
SQL> shutdown immediate; startup; Database closed. Database dismounted. ORACLE instance shut down. SQL> ORACLE instance started. Total System Global Area 413372416 bytes Fixed Size 2289016 bytes Variable Size 322962056 bytes Database Buffers 79691776 bytes Redo Buffers 8429568 bytes Database mounted. Database opened.
6. Verify if you can login into the database directly now.
SQL> connect / as sysdba Connected. SQL>
Conclusion
When the initialization parameter threaded_execution is set to TRUE, it enables the multithreaded Oracle model, operating system authentication is not supported. Attempts to connect to the database using operating system authentication (for example, CONNECT / AS SYSDBA or CONNECT / ) will fail in that case.