If you are using a geodetic coordinate system (8307) a polygon cannot cover more than half the earth.

http://docs.oracle.com/cd/B13789_01/appdev.101/b10826/sdo_cs_concepts.htm#i891851

"No polygon element can have an area larger than one-half the surface of the Earth."

You could try making a multipolygon any time your shape crosses 0 latitude or longitude by splitting your polygon across these boundaries.  You probably have no data large enough to need that treatment, just do it to the map extents polygon.