SQL & PL/SQL :: Accessing V$mystat Gives Table Or View Does Not Exist

I am using the sid of v$mystat to create a unique filename in my pl/sql procedure.

I have granted access to v$mystat to the user that is accessing it from system user as:

SQL>GRANT SELECT ON V_$MYSTAT TO ar;
Grant succeeded.

SQL> commit;

Commit complete.

now when i login as user ar and do a select on v$mystat it works fine:

SQL> select sid from v$mystat WHERE ROWNUM = 1;

SID
----------
290

However, when i do the same from my PL/SQL procedure it throws an error saying :

SQL> @FILECREATE
53 /

Warning: Function created with compilation errors.

SQL> show errors
Errors for FUNCTION FILECREATE:

LINE/COL ERROR
-------- -----------------------------------------------------------------
22/8 PL/SQL: SQL Statement ignored
22/35 PL/SQL: ORA-00942: table or view does not exist

My PL/SQL function can be found as an attachment.