>>I replaced append with insert into command but this doesnt help.
>Some times a day, a duplicate invoice headers will randomly
>appended to file.
>
>Have you looked at the table with no index to see if the record is duplicated, or if the index is corrupted?

I use the following code to dedect duplicate records.
doktyyp c(1) in document type and dokumnr n(7) is document
order number. doktyyp+str(dokumr,7) in unique key for document header.

.... get unique dokumrn and add an invoice header to DOK database

vrecno = recno('dok')
sele 0
use DOK again alias KNDOK
* Check for duplicate record. I thik, if the following locate
* finds duplicate, this is real duplicate, to index corruption.
* there is index on doktyyp+str(dokumnr,7) but recno()!=m.vrecno
* will force actual data check.
locate for recno()!=m.vrecno and ;
doktyyp+str(dokumnr,7)= dok.doktyyp+str(dok.dokumnr,7)

if found()
delete
do logevent with 'Duplicate record is found !!!!!'
endif

Some times per day, logfile shows duplicate records.
Also, without delete, duplicate records are visible in the
database.

>
>The insert command should fix the inherent ambiguity with append blank. I'm still betting on a network client issue. It's amazing what a few tweaks will do. (Novell Client for Netware - adjust "Lock Retries" from 5 to 1, and we've seen 30-50% improvement in speed for our legacy apps)

I have NT and Win 98 clients, NT 4 SP 6 server.
There is nothing to adjust in those clients.