This setting controls the rate at which the query reports system will checkpoint intermediate data to disk while updating the query reports database. This value controls the memory and disk usage of reporting. Setting it too high will increase memory usage as data will build up in memory until it is written out to disk. Setting it too low will increase the amount of intermediate data written out to disk and may increase memory usage at the end of the reports update process when intermediate data is read back in from disk for re-aggregation. It is an advanced setting and care should be taken when modifying its value.
The default setting sets query reporting to checkpoint every 300 log files read: