The PxPlus SQL ODBC driver has some options that may help.
Goto the Options tab of the DSN setup page for the PxPlus ODBC client install. There you will find two options that may help.
Dirty Read - Check box for Dirty Read mode of operation to skip the normal file consistency checks.
Dirty reads can speed file processing by reducing the number of locks issued against a file. However, this may result in inconsistent data should the file be updated while being read by
the PxPlus SQL ODBC Driver.
Burst mode - Check box to enable Burst mode. This helps reduce some of the overhead created by temporary locks.
With Burst mode set, the PxPlus SQL ODBC Driver locks the file header for either 50 file operations or three-tenths of a second, whichever occurs first. This decreases the number of
times the file must be locked and the number of times that internal buffers may need to be reloaded. Refer to the next paragraph below for an explanation on the effect of temporary
locks.
I suspect dirty reads may be of the most help to you.