>I use the code following code (simplified version) to generate primary keys of N(7) type. In one heavy loaded system this code adds duplicate primary keys to DOK table. There are 5-10 duplicate primary keys of one type (from total 50000 keys) in every month.
>
>This system environment:
>
>Windows 2003 terminal server
>Double processor with hyperthreading (task manager shows 4 processors)
>60 terminal server clients calling concurrently this code.
>They all are running single Visual FoxPro 9 application
>
>I tried to replace FLOCK() to RLOCK() but duplicate primary keeys are
>still returned.
>
>How to modify the following code so that duplicate primary keys are not
>returned? I need N(7) type primary keys.
>
>

>* Entry:
>
>* prm_dok C(2) - primary key type to allocate
>
>* KEYS table contains primary key current values:
>*   KeyType C(2) - key type
>*	LastUsed N(7) - last used key value
>
>* Exit:
>
>* dok.dokumnr N(7) contains allocated primary key.
>*   dok.guid containg allocated guid
>
>FUNCTION GetKey( prm_dok )
>
>do while .t.
>  SELECT 0
>  use Keys again alias _keys
>
>  loca for KeyType = m.prm_dok
>  if !found()
>    appe blank
>    repl KeyType with m.prm_dok
>    endif
>
>  LOCAL Last_Used_Key
>  Last_Used_Key = 0
>
>  do while !flock('_keys')
>     wait wind 'waiting for lock' nowa
>     if myinkey()
>       wait clear
>       use in _keys
>       return .F.
>       endif
>
>     on error NOTE
>     = inkey(.1)
>     do seterror
>    enddo
>  wait clear

   && put the flock() before the locate
   && or
   go (recno()) && get latest data from disk


>  Last_Used_Key = max( _keys.LastUsed-1, 0 )
>
>  sele 0
>  use DOK AGAIN
>
>  loca for betw( str(dokumnr,7), str(Last_Used_Key+1,7), ;
>      str(Last_Used_Key+2,7) )
>
>    if found()
>      USE
>      sele _keys
>      repl LastUsed with 0
>      do ReleaseLock
>      loop
>      endif
>
>    use
>    sele DOK
>    repl  dokumnr with Last_Used_Key+1, ;
>       guid with getguid()
>
>  exit
>  enddo
>
>repl LastUsed with Last_Used_Key+2
>do ReleaseLock
>RETURN .T.
>
>PROCEDURE ReleaseLock
>unlock in _keys
>use in _keys
>return
>
>FUNCTION MYINKEY
>priv tul
>on error NOTE
>tul = inkey()
>seterror()
>if type('m.tul')!='N'
>  return .f.
>  endif
>return m.tul == 27
>
>
>PROCEDURE GetGUID
>*DECLARE INTEGER CoCreateGuid IN Ole32.dll STRING @lcGUIDStruc
>*DECLARE INTEGER StringFromGUID2 IN Ole32.dll
>*  STRING cGUIDStruc, STRING @cGUID, LONG nSize
>local cStrucGUID, cGUID, nSize
>cStrucGUID=SPACE(16)
>cGUID=SPACE(80)
>nSize=40
>IF CoCreateGuid(@cStrucGUID) # 0
>  RETURN 'A'+sys(0) +sys(2015)
>  ENDIF
>IF StringFromGUID2(m.cStrucGUID,@cGuid,nSize) = 0
>  RETURN 'B'+sys(0)+sys(2015)
>  ENDIF
>RETURN subs(STRCONV(LEFT(m.cGUID,76),6),2)
>ENDPROC