NLS_LANG parameter issue

@#$%^&amp

Hi While testing some Ukraine characters nls parameter is not working for the session,Kindly help us on this,

select ('vidyaVIDYA') from dual;

select ('1234567890!@#$%^&*()_+') from dual;

select ('й') from dual;

select * from v$nls_parameters where parameter IN ('NLS_TERRITORY','NLS_LANGUAGE','NLS_CHARACTERSET');

ALTER SESSION SET NLS_LANGUAGE='UKRAINIAN';

--ALTER SESSION SET NLS_LANG='UKRAINIAN_UKRAINE.CL8MSWIN1251';

select ('vidyaVIDYA') from dual;

select ('1234567890!@#$%^&*()_+') from dual;

select ('й') from dual;

select * from v$nls_parameters where parameter ='NLS_LANGUAGE';

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Error starting at line 135 in command:

ALTER SESSION SET NLS_LANG = 'UKRAINIAN_UKRAINE.CL8MSWIN1251'