Oracle NLS_ settings

Select * From Nls_Database_Parameters;
Select * From Nls_Instance_Parameters;
Select * From Nls_Session_Parameters;
select * from v$nls_valid_values;

Select value From Nls_Session_Parameters where parameter = 'NLS_SORT';

Alter Session Set Nls_Comp = 'BINARY';
Alter Session Set Nls_Comp = 'LINGUISTIC';
Alter Session Set Nls_Sort = 'BINARY';
Alter Session Set Nls_Sort = 'UNICODE_BINARY';
Alter Session Set Nls_Sort = 'UNICODE_BINARY_CI';
Alter Session Set Nls_Sort = 'BINARY_CI';

Select * From Mloc.T_User Where First_Name = 'делян';
select * from MLOC.t_user where first_name like 'делян';
select * from MLOC.t_user where UPPER(first_name) = UPPER('делян');

Also see: http://www.adp-gmbh.ch/ora/misc/dynamic_performance_views.html