Oracle Spatial User's Guide and Reference - InfoLab

SDO_TUNE.QUALITY_DEGRADATION
Format
Description
Parameters
Usage Notes
SDO_TUNE.QUALITY_DEGRADATION(
schemaname IN VARCHAR2,
indexname IN VARCHAR2
) RETURN NUMBER;
SDO_TUNE.QUALITY_DEGRADATION
Returns the quality degradation for an index or the average quality degradation for
all index tables for an index.
schemaname
Name of the schema that contains the index specified in indexname.
indexname
Name of the spatial R-tree index.
The quality degradation is a number indicating approximately how much longer it
will take to execute the I/O operations of the index portion of any given query with
the current index, compared to executing the I/O operations of the index portion of
the same query when the index was created or most recently rebuilt. For example, if
the I/O operations of the index portion of a typical query will probably take twice
as much time as when the index was created or rebuilt, the quality degradation is 2.
The exact degradation in overall query time is impossible to predict; however, a
substantial quality degradation (2 or 3 or higher) can affect query performance
significantly for large databases, such as those with millions of rows.
Index names are available through the xxx_SDO_INDEX_INFO and xxx_SDO_
INDEX_METADATA views, which are described in Section 2.5.1.
For more information and guidelines relating to R-tree quality and its possible effect
on query performance, see Section 1.7.2.
Spatial Tuning Subprograms 18-11