SQLNET.ALLOWED_LOGON_VERSION_SERVER values

12a For oracle 12.1.0.2 or later connect to server. Password version is 12c
12 For Oracle 11.2.0.3 or later connect to server. Password version is 11g,12C
11 For Oracle 10g or later connect to server. Password version is 10G, 11G, 12C
10 For Oracle 10g or later connect to server. Password version is 10G, 11G, 12C
9 For Oracle 9i or later connect to server. Password version is 10G, 11G, 12C
8 For Oracle 8i or later connect to server. Password version is 10G, 11G, 12C