ORA-01017: invalid username/password; logon denied

 ERROR:

ORA-01017: invalid username/password; logon denied

First of all you need to edit your sqlnet.ora adding (or lowering) the parameter 

SQLNET.ALLOWED_LOGON_VERSION_SERVER to a value below 12. 

But if you try to connect directly after restarting your listener you will receive the 

same ORA-1017 again. The secret is mentioned in the above documentation link as well:

 you will have to recreate the user’s passwords if you need the logon process to work as 

it did work before Oracle Database 12.2.

Behavior difference Oracle 12.1 vs Oracle 12.2

See this simple example after switching SEC_CASE_SENSITIVE_LOGON=FALSE in both databases (as shown above):

Oracle Database 12.1.0.2:

SQL> alter user system identified by oracle;

User altered.

SQL> connect system/oracle

Connected.

Oracle Database 12.2.0.1:

SQL> alter user system identified by oracle;

User altered.

SQL> connect system/oracle

ERROR:

ORA-01017: invalid username/password; logon denied

Warning: You are no longer connected to ORACLE.

[oracle@ora admin]$ cat sqlnet.ora

# sqlnet.ora Network Configuration File: /u01/product/12.2.0/dbhome_1/network/admin/sqlnet.ora

# Generated by Oracle configuration tools.

NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)

ENCRYPTION_WALLET_LOCATION=(SOURCE=(METHOD=FILE)(METHOD_DATA=(DIRECTORY=/u01/product/12.2.0/dbhome_1/admin/DEV/wallet)))

SQLNET.EXPIRE_TIME= 30

SQLNET.ALLOWED_LOGON_VERSION_SERVER=8

SQL> select USERNAME, PASSWORD_VERSIONS from DBA_USERS where USERNAME='SYSTEM';

USERNAME      PASSWORD_VERSIONS

-----------------

SYSTEM          11G 12C

SQL> show parameter sec_case

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

sec_case_sensitive_logon             boolean     TRUE

Solution 

There’s no “10G” mentioned. This will prevent the connection.

Solution: You will have to specify the password again respective ALTER the user(s):

SQL>  alter user system identified by manager;

SQL> select USERNAME, PASSWORD_VERSIONS from DBA_USERS where USERNAME='SYSTEM';

USERNAME     PASSWORD_VERSIONS

-----------------

SYSTEM        10G 11G 12C

Issue  resolved.