How to get rowid of extend

Question

Dear all,
How to get the rowids of the first and last row in every extent by dba_extents?

Answer 1

http://docs.oracle.com/cd/E14072_01/appdev.112/e10577/d_parallel_ex.htm
Examples
The following examples run on the Human Resources (HR) schema of the Oracle Database Sample Schemas. It requires that the HR schema be created with the JOB SYSTEM privilege.
Chunk by ROWID
This example shows the most common usage of this package. After calling the RUN_TASK Procedure, it checks for errors and re-runs in the case of error.
DECLARE
  l_sql_stmt VARCHAR2(1000);
  l_try NUMBER;
  l_status NUMBER;
BEGIN
  -- Create the TASK
  DBMS_PARALLEL_EXECUTE.CREATE_TASK ('mytask');
  -- Chunk the table by ROWID
  DBMS_PARALLEL_EXECUTE.CREATE_CHUNKS_BY_ROWID('mytask', 'HR', 'EMPLOYEES', true, 100);
  -- Execute the DML in parallel
  l_sql_stmt := 'update /*+ ROWID (dda) */ EMPLOYEES e
      SET e.salary = e.salary + 10
      WHERE rowid BETWEEN :start_id AND :end_id';
  DBMS_PARALLEL_EXECUTE.RUN_TASK('mytask', l_sql_stmt, DBMS_SQL.NATIVE,
                                 parallel_level => 10);
  -- If there is an error, RESUME it for at most 2 times.
  L_try := 0;
  L_status := DBMS_PARALLEL_EXECUTE.TASK_STATUS('mytask');
  WHILE(l_try < 2 and L_status != DBMS_PARALLEL_EXECUTE.FINISHED)
  LOOP
    L_try := l_try + 1;
    DBMS_PARALLEL_EXECUTE.RESUME_TASK('mytask');
    L_status := DBMS_PARALLEL_EXECUTE.TASK_STATUS('mytask');
  END LOOP;
  -- Done with processing; drop the task
  DBMS_PARALLEL_EXECUTE.DROP_TASK('mytask');
END;
/