select * from A.test_tbl

select * from test_tbl

alter session set current_schema=A;

SQL> declare
  2     handle int := dbms_sql.open_cursor; 
  3  begin 
  4     dbms_sql.parse (handle, 'select * from bonus', dbms_sql.native); 
  5     dbms_sql.close_cursor (handle); 
  6  exception
  7    when others then 
  8      if dbms_sql.is_open(handle) then dbms_sql.close_cursor (handle); end if;
  9      raise;
 10  end; 
 11  / 
declare
*
ERROR at line 1:
ORA-00942: table or view does not exist
ORA-06512: at line 9

SQL> declare
  2     handle int := dbms_sql.open_cursor; 
  3  begin 
  4     execute immediate 'alter session set current_schema=scott';
  5     dbms_sql.parse (handle, 'select * from bonus', dbms_sql.native); 
  6     dbms_sql.close_cursor (handle); 
  7  exception
  8    when others then 
  9      if dbms_sql.is_open(handle) then dbms_sql.close_cursor (handle); end if;
 10      raise;
 11  end; 
 12  / 

PL/SQL procedure successfully completed.