The housekeeper wash task runs as a low-priority task, and runs only during idle cycles when Adaptive Server has no user tasks to process. While running, the wash task automatically writes dirty buffers to disk (called free writes) and performs other maintenance tasks. These writes result in improved CPU utilization and a decreased need for buffer washing during transaction processing. They also reduce the number and duration of checkpoint spikes— times when the checkpoint process causes a short, sharp rises in disk writes.
Housekeeper garbage collection operates at the priority level of an ordinary user and cleans up data that was logically deleted and resets the rows so the tables have space again.
Use sp_setpsexe to change
the priority of all housekeeper tasks. See Chapter 11, “Diagnosing
System Problems,” in the System Administration Guide: Volume
1 for more information on the housekeeper tasks.
