SAP setting and releasing locks

REPORT  demo_transaction_enqueue MESSAGE-ID sabapdocu.

TABLES  sflight.

DATA  text(8) TYPE c.

DATA  ok_code TYPE sy-ucomm.

CALL SCREEN 100.

MODULE init OUTPUT.
  SET PF-STATUS 'BASIC'.
  sflight-carrid = 'LH'. sflight-connid = '400'.
ENDMODULE.

MODULE exit INPUT.
  LEAVE PROGRAM.
ENDMODULE.

MODULE enqueue INPUT.
  CASE ok_code.
    WHEN 'ENQUEUE'.
      CALL FUNCTION 'ENQUEUE_EDEMOFLHT'
           EXPORTING
                mode_sflight   = 'X'
                carrid         = sflight-carrid
                connid         = sflight-connid
                fldate         = sflight-fldate
           EXCEPTIONS
                foreign_lock   = 1
                system_failure = 2
                OTHERS         = 3.

      CASE sy-subrc.
        WHEN 0.
          MESSAGE i888 WITH 'Enqueue successful'(001).
        WHEN 1.
          text = sy-msgv1.
          MESSAGE e888 WITH 'Record already'(002) 'locked by'(003)
                                                   text.
          CALL TRANSACTION 'SM12'.
        WHEN 2 OR 3.
          MESSAGE e888 WITH 'Error in enqueue!'(004)
                            'SY-SUBRC:' sy-subrc.
      ENDCASE.
    WHEN 'DEQUEUE'.
      CALL FUNCTION 'DEQUEUE_EDEMOFLHT'
           EXPORTING
                mode_sflight = 'X'
                carrid       = sflight-carrid
                connid       = sflight-connid
                fldate       = sflight-fldate
           EXCEPTIONS
                OTHERS       = 1.
      CASE sy-subrc.
        WHEN 0.
          MESSAGE i888 WITH 'Dequeue successful'(005).
        WHEN 1.
          MESSAGE e888 WITH 'Error in dequeue!'(006).
      ENDCASE.
    WHEN 'SM12'.
      CALL TRANSACTION 'SM12'.
  ENDCASE.

ENDMODULE.

MODULE select INPUT.
  CASE ok_code.
    WHEN 'SELECT'.
      SELECT * FROM sflight WHERE carrid = sflight-carrid
                              AND connid = sflight-connid
                              AND fldate = sflight-fldate.
      ENDSELECT.
      MESSAGE i888 WITH 'SY-SUBRC:' sy-subrc.
  ENDCASE.
ENDMODULE.