resource_io_calibrate$

How To Delete Calibrate I/O In The Instance [ID 1393405.1]

Applies to:

Oracle Server - Enterprise Edition - Version 11.2.0.2 to 11.2.0.3 [Release 11.2]
Information in this document applies to any platform.
Reviewed 14-Aug-2012.

Internal comment
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Even if gathering/removal of i/o calibration is under dbperf task, however, this note was been created under PX as using Calibrate I/O is mandatory since 11.2.0.2 release.

Goal

Is it possible to delete Calibrate I/O in the instance?

Fix

Firstly, it needs to define the following definitions:

a) IO specific statistics as part of the system statistics which set stats for single and multi block readtime in millisecond, average multiblock readcount, which is managed by the BMS_STATS.%_SYSTEM_STATS APIs (these statistics help the optimizer to cost row sources e.g. access paths in an execution plan)

and

b) calibrate io statistics is collected for a different purpose, in order to calibrate the I/O capabilities of storage in order to take into account in autodop decesions - this is more a resource management area than the optimizer area.

Given that there is no API to support deleting the io calibration statistics or to restore a values of some earlier calibrations, then with regard to what is happening at SQL level in the dictionary in 11.2.0.2 as part of the calibrate_io call is the following only:

delete from resource_io_calibrate$;
commit;