
Chapter 17. Database performance 567
If RMF shows that the DFW Bypass divided by the total I/O Rate is greater than 1%, that is an
indication of NVS saturation. If this NVS saturation happens, we suggest that you set the
VDWQT to 0 or 1. Setting the VDWQT to 0 does not mean that every record update causes a
write I/O to be triggered. Because, despite the 0% threshold set, the DB2 buffer pool still has
40 buffers set aside. The last recently updated 32 buffers are scheduled for write, which
allows multiple successive updates to the same record to be not written out every time that
record is updated. This method prevents multiple write I/Os to ...