sa_get_dtt_groupreads( dbspace_id )

You can obtain the dbspace_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. If no entries are recorded in this table, typical values are returned. To tailor estimates for your hardware, execute the following statement:

ALTER DATABASE CALIBRATE GROUP READ;

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• SYSDBSPACE system view
• SYSOPTSTAT system view
• ALTER DATABASE statement
• sa_get_dtt system procedure

The following example reports the cost of issuing group reads for the system dbspace.

CALL sa_get_dtt_groupreads( (select dbspace_id from SYSDBSPACE where dbspace_name='system') );