sa_get_dtt_groupreads system procedure

Estimates and reports the cost of issuing group reads on the database server.

Syntax

sa_get_dtt_groupreads( file_id )

You can obtain the file_id from the SYSDBSPACE system view. The estimates returned by the sa_get_dtt_groupreads system procedure are part of the cost model, and are used to select group reads of appropriate sizes during operations such as sorting.

This procedure, intended for internal diagnostic purposes, retrieves data from the ISYSOPTSTAT system table. Rows are not returned if the specified dbspace does not have any estimates recorded in SYSOPTSTAT. To tailor estimates for specific hardware devices, execute the following statement:

ALTER DATABASE CALIBRATE GROUP READ;

Result set

Column name	Data type	Description
GroupSize	UNSIGNED INTEGER	Size, in pages, of disk over which random access takes place.
ReadTime	FLOAT	Amortized cost, in microseconds, of reading one page.