Estimates and reports the cost of issuing group reads on the database server.
sa_get_dtt_groupreads( dbspace_id )
dbspace_id Use this UNSIGNED SMALLINT parameter to specify the database file 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. 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;
|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.|
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