OK - I got a really interesting question down in ABAP General and NW AppSer

Question

This one is so interesting that I thought I'd draw a little extra attention to it here.
See:
Hang on to your hats! (shared buffer in multi-WAS/multi-update process env)
or:
Hang on to your hats! (shared buffer in multi-WAS/multi-update process env)
Any and all <i><b>informed</b></i> opinion welcome.

Answer 1

This is really cool: the <b>export to database</b> statement with a given key value for ID <i><b>replaces</b></i> what's already in the table for the same key value.
To see that this is true, copy the system table INDX to a custom table called ZINDX_QM (so you won't have to change the code below.)  Activate this custom table.
Then run the following code twice as follows:
1) the first time, leave the value of wa_stuff as it is declared, i.e.:
"This is some stuff"
2) the second time, change the value of wa_stuff to:
"This is some stuff - pass 2."
You'll see that the second value has replaced the first value in the custom table.
So the export to database statement actually does <b>a "replace", not an "append"</b>,  if the key value is already in the table.
REPORT  ZFOO.
type-pools: thfb.
TABLES:
  zindx_qm.
DATA:
  context_id             TYPE thfb_context_id,
  cntxt_user_dt(60)      TYPE c,
  cntxtud_s              TYPE string,
  rtrnd_hash             TYPE i,
  rtrnd_hash_n(22)       TYPE n,
  rtrnd_hash_c(22)       TYPE c,
  wa_zindx_qm            TYPE zindx_qm,
  v_chk_cnt              TYPE i,
  wa_stuff(40)           TYPE c VALUE 'This is some stuff - pass 1'.
CALL FUNCTION 'TH_GET_CONTEXT_ID'
  IMPORTING
    CONTEXT_ID       = context_id.
CONCATENATE context_id
            sy-datum
            sy-uname
       INTO cntxt_user_dt.
cntxtud_s = cntxt_user_dt.
CALL FUNCTION 'LCRDB_STRING_HASH'
  EXPORTING
    TEXT =  cntxtud_s
  IMPORTING
    HASH =  rtrnd_hash.
rtrnd_hash_n = rtrnd_hash.
rtrnd_hash_c = rtrnd_hash_n.
wa_zindx_qm-aedat = sy-datum.
wa_zindx_qm-usera = sy-uname.
wa_zindx_qm-pgmid = sy-repid.
EXPORT wa_stuff
  TO DATABASE zindx_qm(mo)
  ID rtrnd_hash_c
  FROM wa_zindx_qm.
CLEAR wa_stuff.
IMPORT wa_stuff TO wa_stuff
  FROM DATABASE zindx_qm(mo)
  ID rtrnd_hash_c.
WRITE: / wa_stuff.
Also, the second cool thing is that the "relid" (area) field of the custom table actually makes coding multiple storage statements much easier.  To see why this is so, just compare what's been commented out in the following BAdI method with what's replaced it:
method IF_EX_INSPECTIONLOT_UPDATE~CREATE_IN_UPDATE.
* 11/10: new export statements from XSQM exit
*EXPORT gt_outtab        TO DATABASE zindx_qm(tb) ID rtrnd_hash_c.
*EXPORT s7_tab_mseg      TO DATABASE zindx_qm(ms) ID rtrnd_hash_c.
*EXPORT v_cntr_recursion TO DATABASE zindx_qm(rc) ID rtrnd_hash_c.
* 11/10 - original decs/imports before switch to database exports from shared buffer exports
*v_memkey(60)      TYPE c,
*v_memkey2(64)     TYPE c,
*v_memkey3(65)     TYPE c,
*v_memkey4(65)     TYPE c,
*v_memkey5(65)     TYPE c,
*v_memkey6(65)     TYPE c,
*IMPORT gt_outtab        TO gt_outtab        FROM SHARED BUFFER indx(st) ID v_memkey.  now tb
*IMPORT s7_tab_mseg      TO s7_tab_mseg      FROM SHARED BUFFER indx(st) ID v_memkey2. now ms
*IMPORT v_cntr_recursion TO v_cntr_recursion FROM SHARED BUFFER indx(st) ID v_memkey3. now rc
*IMPORT v_do_exit        TO v_do_exit        FROM SHARED BUFFER indx(st) ID v_memkey4. now de
*IMPORT wa_zzqa02        TO wa_zzqa02        FROM SHARED BUFFER indx(st) ID v_memkey5. now wz
*IMPORT i_zzqa02         TO i_zzqa02         FROM SHARED BUFFER indx(st) ID v_memkey6. now iz
* for context id typing
TYPE-POOLS:
  thfb.
DATA:
  context_id             TYPE thfb_context_id,
  cntxt_user_dt(60)      TYPE c,
  cntxtud_s              TYPE string,
  rtrnd_hash             TYPE i,
  rtrnd_hash_n(22)       TYPE n,
  rtrnd_hash_c(22)       TYPE c,
  wa_zindx_qm            TYPE zindx_qm,
  v_chk_cnt              TYPE i.
DATA:
  v_do_exit         TYPE c,
  v_cntr_recursion  TYPE i,
  v_itab_cnt        TYPE i,
  v_index           TYPE i,
  v_mapl_cnt        TYPe i.
DATA:
  s_qals            TYPE qals,
  s7_tab_mseg       TYPE STANDARD TABLE OF mseg,
  wa_mseg           TYPE mseg,
  gt_outtab         TYPE STANDARD TABLE OF zzmseg_qm_2007,
  wa_zzqm           TYPE zzmseg_qm_2007,
  wa_zzqa02         TYPE zzqa02_prueflos,
  i_zzqa02          TYPE STANDARD TABLE of zzqa02_prueflos,
  wa_zqm_lottrck    TYPE zqm_lottrck,
  wa_mapl TYPE mapl,
  v_mtart           TYPE mtart,
  v_qmatv           TYPE qmatv.
DATA:
  v_cnt_wyt3        TYPE i,
  v_debug           TYPE i.
  CALL FUNCTION 'TH_GET_CONTEXT_ID'
    IMPORTING
    CONTEXT_ID       = context_id.
  CONCATENATE context_id
              sy-datum
              sy-uname
         INTO cntxt_user_dt.
  cntxtud_s = cntxt_user_dt.
  CALL FUNCTION 'LCRDB_STRING_HASH'
    EXPORTING
      TEXT =  cntxtud_s
    IMPORTING
      HASH =  rtrnd_hash.
  rtrnd_hash_n = rtrnd_hash.
  rtrnd_hash_c = rtrnd_hash_n.
*  CONCATENATE 'DEXIT'
*               sy-uname
*               sy-datum
*               context_id
*          INTO v_memkey4.
*  IMPORT v_do_exit TO v_do_exit FROM SHARED BUFFER indx(st) ID v_memkey4.
  IMPORT v_do_exit TO v_do_exit
    FROM DATABASE zindx_qm(de)
    ID rtrnd_hash_c.
*  CONCATENATE 'CRCSN'
*              sy-uname
*              sy-datum
*              context_id
*         INTO v_memkey3.
*  IMPORT v_cntr_recursion TO v_cntr_recursion FROM SHARED BUFFER indx(st) ID v_memkey3.
  IMPORT v_cntr_recursion TO v_cntr_recursion
    FROM DATABASE zindx_qm(rc)
    ID rtrnd_hash_c.
*  CONCATENATE sy-uname
*              sy-datum
*              context_id
*         INTO v_memkey.
*  IMPORT gt_outtab TO gt_outtab FROM SHARED BUFFER indx(st) ID v_memkey.
  IMPORT gt_outtab TO gt_outtab
    FROM DATABASE zindx_qm(tb)
    ID rtrnd_hash_c.
  DESCRIBE TABLE gt_outtab LINES v_itab_cnt.
  IF v_do_exit = 'N'.
    v_do_exit = 'Y'.
*    EXPORT v_do_exit FROM v_do_exit TO SHARED BUFFER indx(st) ID v_memkey4.
    EXPORT v_do_exit FROM v_do_exit TO DATABASE zindx_qm(de) ID rtrnd_hash_c.
*    CONCATENATE 'SQALS'
*                sy-uname
*                sy-datum
*                context_id
*           INTO v_memkey5.
*    IMPORT wa_zzqa02 TO wa_zzqa02 FROM SHARED BUFFER indx(st) ID v_memkey5.
    IMPORT wa_zzqa02 TO wa_zzqa02
      FROM DATABASE zindx_qm(wz)
      ID rtrnd_hash_c.
    IF v_cntr_recursion < v_itab_cnt.
*    CONCATENATE 'TQALS'
*                sy-uname
*                sy-datum
*                context_id
*           INTO v_memkey6.
*      IMPORT i_zzqa02 TO i_zzqa02 FROM SHARED BUFFER indx(st) ID v_memkey6.
      IMPORT i_zzqa02 TO i_zzqa02
        FROM DATABASE zindx_qm(iz)
        ID rtrnd_hash_c.
    ENDIF.
    APPEND wa_zzqa02 TO i_zzqa02.
*    EXPORT i_zzqa02 FROM i_zzqa02 TO SHARED BUFFER indx(st) ID v_memkey6.
    EXPORT i_zzqa02 FROM i_zzqa02 TO DATABASE zindx_qm(iz) ID rtrnd_hash_c.
    IF v_cntr_recursion = 0.
      CALL FUNCTION 'ZZQA02_ASSIGN_BDC' IN BACKGROUND TASK.
    ENDIF.
    EXIT.
  ENDIF.
*  CONCATENATE 'MSEG'
*              sy-uname
*              sy-datum
*              context_id
*         INTO v_memkey2.
*  IMPORT s7_tab_mseg TO s7_tab_mseg FROM SHARED BUFFER indx(st) ID v_memkey2.
  IMPORT s7_tab_mseg TO s7_tab_mseg
    FROM DATABASE zindx_qm(ms)
    ID rtrnd_hash_c.
  v_index = v_itab_cnt - v_cntr_recursion + 1.
  READ TABLE gt_outtab INTO wa_zzqm INDEX v_index.
  READ TABLE s7_tab_mseg INTO wa_mseg INDEX v_index.
  IF    wa_mseg-bwart <> '101'
    AND wa_mseg-bwart <> '103'.
    EXIT.
  ENDIF.
  IF  wa_mseg-werks <> '2000'.
    EXIT.
  ENDIF.
  SELECT
  SINGLE mtart
    FROM mara
    INTO v_mtart
   WHERE matnr = wa_mseg-matnr.
  SELECT
  SINGLE qmatv
   FROM  marc
   INTO  v_qmatv
  WHERE  matnr = wa_mseg-matnr
    AND  werks = wa_mseg-werks.
  IF    v_mtart <> 'ROH'
    AND v_qmatv <> 'X'.
    EXIT.
  ENDIF.
  s_qals = insplot.
*  v_lifnr_save = s_qals-lifnr.
  CALL FUNCTION 'QPBU_LOT_DELETE'
     EXPORTING
     I_QALS        = s_qals.
   s_qals-lifnr   = wa_zzqm-zzlifnr.
   s_qals-pplverw = '5'.
   s_qals-stat19  = 'X'.
  SELECT
  SINGLE plnty
         plnnr
         plnal
         zkriz
         zaehl
    FROM mapl
    INTO (s_qals-plnty,
          s_qals-plnnr,
          s_qals-plnal,
          s_qals-zkriz,
          s_qals-zaehl)
   WHERE matnr = wa_mseg-matnr
     AND werks = wa_mseg-werks
     AND lifnr = wa_zzqm-zzlifnr.
  v_do_exit = 'N'.
*  EXPORT v_do_exit FROM v_do_exit TO SHARED BUFFER indx(st) ID v_memkey4.
  EXPORT v_do_exit FROM v_do_exit TO DATABASE zindx_qm(de) ID rtrnd_hash_c.
  v_cntr_recursion = v_cntr_recursion - 1.
*  EXPORT v_cntr_recursion FROM v_cntr_recursion TO SHARED BUFFER indx(st) ID v_memkey3.
  EXPORT v_cntr_recursion FROM v_cntr_recursion TO DATABASE zindx_qm(rc) ID rtrnd_hash_c.
  wa_zzqa02-prueflos = s_qals-prueflos.
*  CONCATENATE 'SQALS'
*              sy-uname
*              sy-datum
*              context_id
*         INTO v_memkey5.
*  EXPORT wa_zzqa02 FROM wa_zzqa02 TO SHARED BUFFER indx(st) ID v_memkey5.
  EXPORT wa_zzqa02 FROM wa_zzqa02 TO DATABASE zindx_qm(wz) ID rtrnd_hash_c.
  SELECT COUNT( * )
    FROM mapl
    INTO v_mapl_cnt
   WHERE matnr = wa_mseg-matnr
     AND werks = wa_mseg-werks
     AND plnty = 'Q'
     AND plnnr <> '99999999'.
  IF v_mapl_cnt = 1.
    wa_mapl-matnr = wa_mseg-matnr.
    wa_mapl-werks = wa_mseg-werks.
    wa_mapl-plnty = 'Q'.
    wa_mapl-plnnr = '99999999'.
    wa_mapl-plnal = '01'.
    wa_mapl-zkriz = '0000001'.
    wa_mapl-zaehl = '00000001'.
    wa_mapl-lifnr = 'ZZZZZZZZZZ'.
    wa_mapl-datuv = sy-datum.
    INSERT INTO mapl VALUES wa_mapl.
  ENDIF.
  CALL FUNCTION 'QPBU_LOT_INSERT'
     EXPORTING
       QALS_NEW       = s_qals.
  IF wa_zzqm-zzltno IS INITIAL.
    EXIT.
  ENDIF.
  wa_zqm_lottrck-zzltno   = wa_zzqm-zzltno.
  wa_zqm_lottrck-werk     = wa_mseg-werks.
  wa_zqm_lottrck-prueflos = s_qals-prueflos.
  wa_zqm_lottrck-mblnr    = s_qals-mblnr.
  wa_zqm_lottrck-mjahr    = s_qals-mjahr.
  wa_zqm_lottrck-zeile    = s_qals-zeile.
  INSERT
    INTO zqm_lottrck
  VALUES wa_zqm_lottrck.
ENDMETHOD.