>>>Hi All:
>>>
>>>Every time I run a transaction, my program either APPENDs BLANK to a log table, or updates an existing record in the log table.
>>>
>>>What is the best resource to consult with regard to doing this in a multiuser environment?
>>>
>>>Thanks,
>>>
>>>Yossi
>>
>>Don't use Append Blank, use Insert Into instead, this is especially important in a multiuser environment. And in general you should never update a record in a log table, you should only add new records.
>
>Are you saying that with INSERT INTO, I don't need flock()?
>I guess that 'Log file' is inaccurate. It's a list of emails that have a lSent field. If the previous attempt was unsuccessful and it is successful now, I want to update the lSent to .t.
>
>

>PROCEDURE UpdateEmailLog(tcText, tcCustno, tcDisposition)
>
>LOCAL lnSelect, llUpdated
>
>lnSelect = SELECT()
>
>SELECT emails
>
>llUpdated = .F.
>
>DO WHILE !llUpdated
>
>	IF FLOCK()
>		APPEND BLANK
>		REPLACE em_body WITH tcText, ;
>			em_datetim WITH DATETIME(), ;
>			em_custno WITH tcCustno, ;
>			em_disptn WITH tcDisposition
>
>		UNLOCK
>		llUpdated = .t.
>	ENDIF
>
>ENDDO
>
>
>SELECT (lnSelect)
>
>RETURN
>

This will show you a much better code. Append Blank followed by Replace is bad, you should never use it again! Instead use Insert as I told you earlier.

Function UpdateEmailLog(tcText, tcCustno, tcDisposition)
   Local llSuccess As Boolean, ;
      lnSelect As Number, ;
      lnX As Number
   m.lnSelect = Select()
   m.llSuccess = .F.
   For m.lnX = 1 To 10
      Try
         Insert Into emails (em_body, em_datetim) Values m.tcText, Datetime()
         m.llSuccess = .T.
         Exit
      Catch
      Endtry
   Endfor
   Select(m.lnSelect)
Return m.llSuccess

Note that this is a function, not a procedure. The advantage is that you can check the return value, if it's .F. something went wrong. I also specified a maximum number of tries, to avoid that the system hangs if something fails.

One last note about using flock(). I checked all the programs I have created over the last 25 years, and I never use flock! The only place I use the sibling, rlock(), is in my procedure to calculate the next number which has to be in sequence, for instance an invoice number.