Explanation/Reference:
AD: There are two sets of spatial index metadata views for each schema (user): xxx_SDO_INDEX_INFO and xxx_SDO_INDEX_METADATA, where xxx can be USER or ALL. These views are read-only to users; they are created and maintained by the Spatial indexing routines.
C: USER_SDO_GEOM_METADATA contains metadata information for all spatial tables owned by the user (schema). This is the only view that you can update, and it is the one in which Spatial users must insert metadata related to spatial tables.
References: https://docs.oracle.com/cd/B28359_01/appdev.111/b28400/
sdo_objrelschema.htm#SPATL545