I was having fun with Oracle Spatial lately, and stumbled over a fantastic bug (which should have been already fix what he not is...). I got the following:

ORA-29902: error in executing ODCIindexStart()routine ORA-13207: incorrect use of ... ORA-06512: at "MYSYS.SDO_INDEX_METHOD_10I...

which was caused by

AND SDO_ANYINTERACT(XSP.GEOM,XCG.GEOM) = 'FALSE'

what I really like here is the solution, which really works

AND SDO_ANYINTERACT(XSP.GEOM,XCG.GEOM) != 'TRUE'

This bug (18718478) should be solved (at least for SDO_RELATE) with 12.1.0.2 which I am currently working on...