To determine the number of significant decimal digits of precision, try something like the following using long/lat values are are representative of the data you want to load.
select sdo_geom.sdo_distance(sdo_geometry(2001,8307,sdo_point_type(-147,-32,null),null,null),
sdo_geometry(2001,8307,sdo_point_type(-147,-32.0000001,null),null,null),
0.005
) as dist
from dual;
-- Results
--
DIST
----------
0.01111950562
--
-- In this situation, 1cm will be maintained at roughly 7 digits of precision (latitude).
--
select sdo_geom.sdo_distance(sdo_geometry(2001,8307,sdo_point_type(-147,-32,null),null,null),
sdo_geometry(2001,8307,sdo_point_type(-147.0000001,-32,null),null,null),
0.005
) as dist
from dual;
-- Results
--
DIST
----------
0.009429874745
--
-- Roughly the same.
You can, of course, create two points 0.01m apart in a planar projection (eg UTM) in your area, and convert to 8307 and subtract the values to get the number of decimal digits of degrees difference.
regards
Simon
Edited by: Simon Greener on Mar 21, 2013 1:44 PM