ompio has historically changed the WRONLY flag provided by the applicaiton
to RDWR to allow for the data sieving optimization within the two-phase I/O
fcoll component. This change did not have a performance impact
on regular UNIX file systems, but seems to hurt performance on NFS (and maybe Lustre?)
So provide an option that allows to keep the WRONLY option, and raise an error
if tha fcoll/two-phase would actually like to use the data sieving.
Signed-off-by: Edgar Gabriel <egabriel@central.uh.edu>
75ab006ec0