Changing NLS_Language NLS_Territory NLS_Calendar

Bismillahir Rahmanir Raheem

When I installed my Oracle database I probably selected US or I think default installation is US.
But you can change it as you like later
We will  see how to change it

You can see all your NLS_parameters from a dynamic view called NLS_Parameters

select *
from NLS_Parameters;

You will see in the results parameters like
NLS_Language    AMERICAN
NLS_Calendar    GREGORIAN
NLS_Territory     AMERICA

and others

so lets change the default values

alter session set NLS_Language='Arabic';

alter session set NLS_Territory='United Arab Emirates';

alter session set NLS_Calendar='Arabic Hijrah';


 Similarly you can change any NLS_parameters as you like

You might  want to know what are the values that you can assign to these NLS parameters

here is link to oracle documentation to help you

Oracle Database Globalization Support