PARALLEL_IO_CAP_ENABLED

Property	Description
Parameter type	Boolean
Default value	false
Modifiable	ALTER SESSION, ALTER SYSTEM
Range of values	true | false
Basic	No
Real Application Clusters	Multiple instances can have different values.

PARALLEL_IO_CAP_ENABLED specifies whether or not Oracle caps the default degree of parallelism to no greater than what the I/O system can support. This new value is calculated based on the results of the resource manager's I/O calibration package.

If PARALLEL_IO_CAP_ENABLED is set to true and the database I/O capacity has been calibrated, then Oracle will reduce the default degree of parallelism if the I/O capacity cannot support the available number of CPUs. To calibrate the I/O capacity, use the DBMS_RESOURCE_MANAGER.CALIBRATE_IO procedure to measure the system's I/O capacity. Oracle then computes the degree of parallelism so as not to exceed the system's I/O capacity.

Note:

1. This parameter was introduced in 11g.

2. Query for the current value of the parameter

select name, value, isdefault, isses_modifiable, issys_modifiable,

isinstance_modifiable, isdeprecated, description

from v$parameter where upper(name) = ‘PARALLEL_IO_CAP_ENABLED’;

NAME	VALUE	IS DEFAULT	ISSES_ MODIFIABLE	ISSYS_ MODIFIABLE		ISINSTANCE_ MODIFIABLE	IS DEPRECATED	DESCRIPTION
parallel_io_cap_enabled	FALSE	TRUE	TRUE	IMMEDIATE	TRUE		FALSE	enable capping DOP by IO bandwidth

Oracle initializatoin parameters