Managing Parallel Processing

Oracle Data Miner workflows and views, and most Data Mining algorithms, can take advantage of parallel processing of queries when it is enabled in the database. Parameters in INIT.ORA control the behavior of parallel processing. By default parallelism is disabled (PARALLEL_DEGREE_POLICY=MANUAL).

Parallel processing of queries can be system-determined, or it can be set to Degree of Parallelism. When parallel processing is system-determined, the database dynamically determines Degree of Parallelism values for all SQL statements.

The parallel feature of Oracle Database is designed to use maximum resources assuming the operation will finish faster if you use more resources. In a multiuser environment, increasing the use of parallelism can rapidly deplete system resources, reducing resources for other users to execute parallel statements concurrently.

Oracle Data Miner workflows support a parallel query feature, which allows users to manually enable parallel processing for specific nodes or entire workflows. You can disable this feature by setting the Oracle Data Miner repository property PARALLEL_QUERY_ON_ALLOWED to FALSE. By default, this property is set to TRUE. Example 6-4 shows how to disable the parallel query processing feature of Oracle Data Miner.

The Oracle Data Miner model build process can generate many parallel sessions if your database configuration allows for it. To limit the impact on the overall system, you should implement an appropriate resource plan and, if necessary, prevent users from setting parallel query within their Data Miner sessions.

See Also:

Oracle Database VLDB and Partitioning Guide for an introduction to parallel processing

Example 6-4 Disabling the Parallel Query Feature for Oracle Data Miner Workflows and Nodes

connect sys as sysdba;
Enter password: password
-- value of PARALLEL_QUERY_ON_ALLOWED before update
SELECT property_name, property_str_value 
   FROM ODMRSYS.ODMR$REPOSITORY_PROPERTIES
   WHERE property_name = 'PARALLEL_QUERY_ON_ALLOWED';
-- update PARALLEL_QUERY_ON_ALLOWED
UPDATE ODMRSYS.ODMR$REPOSITORY_PROPERTIES
   SET property_str_value = 'FALSE'
   WHERE property_name = 'PARALLEL_QUERY_ON_ALLOWED';
-- commit change
COMMIT;
-- verify value of PARALLEL_QUERY_ON_ALLOWED after update
SELECT property_name, property_str_value 
   FROM ODMRSYS.ODMR$REPOSITORY_PROPERTIES
   WHERE property_name = 'PARALLEL_QUERY_ON_ALLOWED';

connect sys as sysdba;
Enter password: password
-- value of PARALLEL_QUERY_ON_ALLOWED before update
SELECT property_name, property_str_value 
   FROM ODMRSYS.ODMR$REPOSITORY_PROPERTIES
   WHERE property_name = 'PARALLEL_QUERY_ON_ALLOWED';
-- update PARALLEL_QUERY_ON_ALLOWED
UPDATE ODMRSYS.ODMR$REPOSITORY_PROPERTIES
   SET property_str_value = 'FALSE'
   WHERE property_name = 'PARALLEL_QUERY_ON_ALLOWED';
-- commit change
COMMIT;
-- verify value of PARALLEL_QUERY_ON_ALLOWED after update
SELECT property_name, property_str_value 
   FROM ODMRSYS.ODMR$REPOSITORY_PROPERTIES
   WHERE property_name = 'PARALLEL_QUERY_ON_ALLOWED';