Question about "Croning an Export" ...

I'm a consultant at a shop here in South Carolina ... I've pretty much got their shop
in order, so that I can go on to my next job ... The one thing I don't have:

I want an Export to occur each night before they run their backups ... That way,
(becuase of the way I've set up the backups), they will have both their data in normal
form (i.e. dbf and control files) and in data form (in case their structure would
"screq" up, they still won't lose any data!) So I'd like to cron a Export job to run
automatically every night before the backups ...

The problem is that I've tried it and, for some reason, it asks for a password, even
though I've supplied it (via the USERID parm) in a parm file ... I execute it a follows:

"/apps/oracle/product/7.1.6/bin/exp parfile="Database_Export.par"

and I've even tried it by putting the userid on the outside ...

ANY suggestions?! Please!!

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Brad Puett
bpuett_at_interpath.com