V$views not available in PL/SQL scripts why?

Question

I created a procedure as follows
create or replace procedure log_user_count
     (pi_directory in varchar2, pi_file_name in varchar2)
as
     v_file_handle utl_file.file_type;
     v_user_count number;
begin
     execute immediate 'select count(*) from v$session where username is not null' into v_user_count;
     v_file_handle := utl_file.fopen(pi_directory, pi_file_name, 'A');
     utl_file.new_line(v_file_handle);
     utl_file.put_line(v_file_handle, '--- User Log --- ');
     utl_file.new_line(v_file_handle);
     utl_file.put_line(v_file_handle, ' on ' || to_char(sysdate, 'MM/DD/YYYY HH24:MI'));
     utl_file.put_line(v_file_handle, 'Number of users logged on : '||v_user_count);
     utl_file.put_line(v_file_handle , ' --- End Log --- ');
     utl_file.new_line(v_file_handle);
     utl_file.fclose(v_file_handle);
exception
     when utl_file.invalid_filename then
          dbms_output.put_line('File is invalid');
     when utl_file.write_error then
          dbms_output.put_line('Oracle is not able to write to file');
end;
Procedure was created without any errors but when executed I got an error message showing the table or view is not present.
When I tried with user tables I got successful completion of the plsql procedure.
Why it happened? How can I correct the error? Plz advice.

Answer 1

And you give the grant to V_$SESSION because V$SESSION is a synonym...
SYS@DEMO102> grant select on v$session to scott;
grant select on v$session to scott
ERROR at line 1:
ORA-02030: can only select from fixed tables/views
SYS@DEMO102> select * from dba_synonyms where synonym_name = 'V$SESSION';
OWNER                          SYNONYM_NAME
TABLE_OWNER                    TABLE_NAME
DB_LINK
PUBLIC                         V$SESSION
SYS                            V_$SESSION
SYS@DEMO102> grant select on v_$session to scott;
Grant succeeded.
SYS@DEMO102> Nicolas.