11 SEM_PERF Package Subprograms

The SEM_PERF package contains subprograms for examining and enhancing the performance of the Resource Description Framework (RDF) and Web Ontology Language (OWL) support in an Oracle database. To use the subprograms in this chapter, you must understand the conceptual and usage information in Chapter 1, "Oracle Database Semantic Technologies Overview" and Chapter 2, "OWL Concepts".

This chapter provides reference information about the subprograms, listed in alphabetical order.

SEM_PERF.GATHER_STATS

Format

SEM_PERF.GATHER_STATS();

just_on_values_table IN BOOLEAN DEFAULT FALSE,

degree IN NUMBER(38) DEFAULT NULL);

Description

Gathers statistics about RDF and OWL tables and their indexes.

Parameters

just_on_values_table

TRUE collects statistics only on the table containing the lexical values of triples; FALSE (the default) collects statistics on all major tables related to the storage of RDF and OWL data.

A value of TRUE reduces the execution time for the procedure; and it may be sufficient if you need only to collect statistics on the values table (for example, if you use other interfaces to collect any other statistics that you might need).

degree

Degree of parallelism. For more information about parallel execution, see Oracle Database VLDB and Partitioning Guide.

Usage Notes

To use this procedure, you must connect as a user with permission to execute it. By default, when Spatial is installed as part of Oracle Database, only the MDSYS user can execute this procedure; however execution permission on this procedure can be granted to users as needed.

This procedure collects statistical information that can help you to improve inferencing performance, as explained in Section 2.2.7. This procedure internally calls the DBMS_STATS.GATHER_TABLE_STATS procedure to collect statistics on RDF- and OWL-related tables and their indexes, and stores the statistics in the Oracle Database data dictionary. For information about using the DBMS_STATS package, see Oracle Database PL/SQL Packages and Types Reference.

Gathering statistics uses significant system resources, so execute this procedure when it cannot adversely affect essential applications and operations.

Examples

The following example gathers statistics about RDF and OWL related tables and their indexes.

EXECUTE SEM_PERF.GATHER_STATS;