Oracle Spatial Geometry Type
Oracle Spatial supports object relational model for representing geometry. Geometry is stored in native spatial data type MDSYS.SDO_GEOMETRY.
Oracle Geometry Metadata Views
To create an Spatial Index for an SDO_GEOMETRY column there has to be a row in USER_SDO_GEOM_METADATA view.
Row in USER_SDO_GEOM_METADATA contains Table Name, Column Name of geometry, information about lower and upper bound of every dimension, tolerance of every dimension and SRID Coordinate System (Spatial Reference System) identifier.
Oracle Spatial Index
Oracle Spatial lets you create Spatial Index on geometry column. For Spatial Index R-tree indexing is used (Oracle supports also quadtree indexing but it is discouraged). Spatial Index has layer geometry type parameter which defines which type of geometries are included in layer. It can be point, line, polygon or combination of those.
SRID
An SRID (Spatial Reference Identifier) is an integer value a key to MDSYS.CR_SYS table describing coordinate systems. If no coordinate system is defined SRID is NULL value.
