Databases Reference
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(that is, the propagation time) are in the same range as disk I/O times, and need to be
considered in the estimate of total response time.
For LANs where network distances may be less than .1 km, the dominating delay is
transmission time, but neither time in this example is significant compared to typical
disk I/O times. Thus, in LANs we can consider network delays to be negligible unless
there are extremely large packets or trains of packets.
A.4
CPU Time Delays
CPU time delays are mainly dependent on the processing required by the database appli-
cation, and are largely independent of the I/O operations. Those CPU delays caused by
the software to manage the I/O are usually negligible compared to the I/O times, and are
even further diminished when they overlap the I/O operations. Our model assumes data-
base systems to be I/O-bound and considers CPU delays as negligible.
