Hi,
Either disable disk caching on the server (quick fix) or use the Updated Flush command in VFP9, it flushes the file back to disk ensuring sync between the cache and the disk.

Hope this helps.

P.S. On a highly loaded system I have seen the OS drop a dirty cache without ensuring that it was written back to disk.

>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
>
>  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