Enque and Deque

Question

Hi all,
Can any one explain with example how to use Enque and Deque to lock a database table?

Answer 1

this editable alv using this to make change in standard table.
*& Report  ZALVF
REPORT  ZALVF.
TYPE-POOLS                                                      *
TYPE-POOLS: SLIS.
INTERNAL TABLES/WORK AREAS/VARIABLES     *
DATA: I_FIELDCAT TYPE SLIS_T_FIELDCAT_ALV,
      I_INDEX TYPE STANDARD TABLE OF I WITH HEADER LINE,
      W_FIELD TYPE SLIS_FIELDCAT_ALV,
      P_TABLE LIKE DD02L-TABNAME,
      DY_TABLE TYPE REF TO DATA,
      DY_TAB TYPE REF TO DATA,
      DY_LINE TYPE REF TO DATA.
FIELD-SYMBOLS                                                   *
FIELD-SYMBOLS: <DYN_TABLE> TYPE STANDARD TABLE,
               <DYN_WA> TYPE ANY,
               <DYN_FIELD> TYPE ANY,
               <DYN_TAB_TEMP> TYPE STANDARD TABLE.
SELECTION SCREEN                                                *
PARAMETERS: TABNAME(30) TYPE C,
            LINES(100)  TYPE N.
START-OF-SELECTION                                              *
START-OF-SELECTION.
Storing table name
  P_TABLE = TABNAME.
Create internal table dynamically with the stucture of table name
entered in the selection screen
  CREATE DATA DY_TABLE TYPE STANDARD TABLE OF (P_TABLE).
  ASSIGN DY_TABLE->* TO <DYN_TABLE>.
  IF SY-SUBRC <> 0.
    MESSAGE I000(Z_ZZZ_CA_MESSAGES) WITH ' No table found'.
    LEAVE TO LIST-PROCESSING.
  ENDIF.
Create workarea for the table
  CREATE DATA DY_LINE LIKE LINE OF <DYN_TABLE>.
  ASSIGN DY_LINE->* TO <DYN_WA>.
Create another temp. table
  CREATE DATA DY_TAB TYPE STANDARD TABLE OF (P_TABLE).
  ASSIGN DY_TAB->* TO <DYN_TAB_TEMP>.
  SORT I_FIELDCAT BY COL_POS.
Select data from table
  SELECT * FROM (P_TABLE)
  INTO TABLE <DYN_TABLE>
  UP TO LINES ROWS.
  REFRESH <DYN_TAB_TEMP>.
Display report
  CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
    EXPORTING
      I_CALLBACK_PROGRAM       = SY-REPID
      I_STRUCTURE_NAME         = P_TABLE
      I_CALLBACK_USER_COMMAND  = 'USER_COMMAND'
      I_CALLBACK_PF_STATUS_SET = 'SET_PF_STATUS'
    TABLES
      T_OUTTAB                 = <DYN_TABLE>
    EXCEPTIONS
      PROGRAM_ERROR            = 1
      OTHERS                   = 2.
  IF SY-SUBRC <> 0.
  ENDIF.
*&      Form  SET_PF_STATUS
      Setting custom PF-Status
     -->RT_EXTAB   Excluding table
FORM SET_PF_STATUS USING RT_EXTAB TYPE SLIS_T_EXTAB.
  SET PF-STATUS 'Z_STANDARD'.
ENDFORM.                    "SET_PF_STATUS
*&      Form  user_command
      Handling custom function codes
     -->R_UCOMM      Function code value
     -->RS_SELFIELD  Info. of cursor position in ALV
FORM USER_COMMAND  USING    R_UCOMM LIKE SY-UCOMM
                  RS_SELFIELD TYPE SLIS_SELFIELD.
Local data declaration
  DATA: LI_TAB TYPE REF TO DATA,
        L_LINE TYPE REF TO DATA.
Local field-symbols
  FIELD-SYMBOLS:<L_TAB> TYPE TABLE,
                <L_WA>  TYPE ANY.
Create table
  CREATE DATA LI_TAB TYPE STANDARD TABLE OF (P_TABLE).
  ASSIGN LI_TAB->* TO <L_TAB>.
Create workarea
  CREATE DATA L_LINE LIKE LINE OF <L_TAB>.
  ASSIGN L_LINE->* TO <L_WA>.
  CASE R_UCOMM.
  When a record is selected
    WHEN '&IC1'.
    Read the selected record
      READ TABLE <DYN_TABLE> ASSIGNING <DYN_WA> INDEX
      RS_SELFIELD-TABINDEX.
      IF SY-SUBRC = 0.
      Store the record in an internal table
        APPEND <DYN_WA> TO <L_TAB>.
      Fetch the field catalog info
        CALL FUNCTION 'REUSE_ALV_FIELDCATALOG_MERGE'
          EXPORTING
            I_PROGRAM_NAME         = 'Z_DEMO_PDF_JG'
            I_STRUCTURE_NAME       = P_TABLE
          CHANGING
            CT_FIELDCAT            = I_FIELDCAT
          EXCEPTIONS
            INCONSISTENT_INTERFACE = 1
            PROGRAM_ERROR          = 2
            OTHERS                 = 3.
        IF SY-SUBRC = 0.
        Make all the fields input enabled except key fields
          W_FIELD-INPUT = 'X'.
          MODIFY I_FIELDCAT FROM W_FIELD TRANSPORTING INPUT
          WHERE KEY IS INITIAL.
        ENDIF.
      Display the record for editing purpose
        CALL FUNCTION 'REUSE_ALV_LIST_DISPLAY'
          EXPORTING
            I_CALLBACK_PROGRAM    = SY-REPID
            I_STRUCTURE_NAME      = P_TABLE
            IT_FIELDCAT           = I_FIELDCAT
            I_SCREEN_START_COLUMN = 10
            I_SCREEN_START_LINE   = 15
            I_SCREEN_END_COLUMN   = 200
            I_SCREEN_END_LINE     = 20
          TABLES
            T_OUTTAB              = <L_TAB>
          EXCEPTIONS
            PROGRAM_ERROR         = 1
            OTHERS                = 2.
        IF SY-SUBRC = 0.
        Read the modified data
          READ TABLE <L_TAB> INDEX 1 INTO <L_WA>.
        If the record is changed then track its index no.
        and populate it in an internal table for future
        action
          IF SY-SUBRC = 0 AND <DYN_WA> <> <L_WA>.
            <DYN_WA> = <L_WA>.
            I_INDEX = RS_SELFIELD-TABINDEX.
            APPEND I_INDEX.
          ENDIF.
        ENDIF.
      ENDIF.
  When save button is pressed
    WHEN 'SAVE'.
    Sort the index table
      SORT I_INDEX.
    Delete all duplicate records
      DELETE ADJACENT DUPLICATES FROM I_INDEX.
      LOOP AT I_INDEX.
      Find out the changes in the internal table
      and populate these changes in another internal table
        READ TABLE <DYN_TABLE> ASSIGNING <DYN_WA> INDEX I_INDEX.
        IF SY-SUBRC = 0.
          APPEND <DYN_WA> TO <DYN_TAB_TEMP>.
        ENDIF.
      ENDLOOP.
    Lock the table
      CALL FUNCTION 'ENQUEUE_E_TABLE'
        EXPORTING
          MODE_RSTABLE   = 'E'
          TABNAME        = P_TABLE
        EXCEPTIONS
          FOREIGN_LOCK   = 1
          SYSTEM_FAILURE = 2
          OTHERS         = 3.
      IF SY-SUBRC = 0.
      Modify the database table with these changes
        MODIFY (P_TABLE) FROM TABLE <DYN_TAB_TEMP>.
        REFRESH <DYN_TAB_TEMP>.
      Unlock the table
        CALL FUNCTION 'DEQUEUE_E_TABLE'
          EXPORTING
            MODE_RSTABLE = 'E'
            TABNAME      = P_TABLE.
      ENDIF.
      RS_SELFIELD-REFRESH = 'X'.
    WHEN 'EXIT'.
      LEAVE PROGRAM.
  ENDCASE.
ENDFORM.                    "user_command