TPDC Manual (G06.24+)

Using the SPAM Performance Data Charts and
Reports
Tandem Performance Data Collector (TPDC) Manual—526357-001
5-14
Disc File I/O Activity Distribution (DFIODST)
page 1
Disc File I/O Activity Distribution for System \CSO (Release D20)
-----------------------------------
__________________________________________________________________________
| CPU's | | VOLUME's | | FILE's |ESTIMATED
| % of | | % of | | % of |UTILIZATN
| TOTAL | | CPU | | VOLUME | SHIFT
Cpu Chit DIOs $Volume Chits DIOs Subvol .Filename Chits DIOs Cpu Disc
--- ====+==== -------- =====+===== ----------------- =====+===== ---- ----
This report shows the estimated effects of disc file (or
partition) I/O activity on CPUs and disc drives.
The report presents the 'CPU -> Disc -> File' hierarchy, with
the most 'active' entity at each level shown first. That is,
the first CPU shown is that with the highest sum of Cache Hits
and Disc I/Os (its percentages of the system-wide totals of
each of these values is shown). The first Disc Volume shown
for each CPU is that with the highest sum of Cache Hits and
Disc I/Os within its CPU (its percentage of the CPU's totals
of each of these values is also shown). The first File (or
Partition) shown for each Disc Volume is that with the highest
total 'Driver Calls' on the Volume (again, its percentage of
the Volume's totals of Cache Hits and [Driver Calls minus
Cache Hits] is also shown). Progressively less active Files
or Partitions on the Volume are then shown, followed by
progressively less active Volumes within the CPU, followed by
progressively less active CPUs.
'Estimated Utilization Shift' represents the estimated amounts
by which the utilizations of the Disc Volume's primary CPU
(Cpu) and primary drive (Disc) would drop if the file or
partition were moved entirely off its current Disc Volume to
a Volume primaried in a different CPU. If the Volume is
mirrored, the mirror drive's utilization would normally be
expected to drop by an amount similar to the primary drive's.
These are 'absolute' values; that is, a 'Cpu' value of (for
example) 12.7 means that the CPU utilization would drop from
(for example) 52.7% to 40.0% if the file were moved.
The utilizations of the primary CPU and drive(s) to which the
file or partition is moved could normally be expected to
increase by similar amounts, if work were to continue to be
processed at the same rate following the move. Such, of
course, may not be the case.
The CPU utilization shift is estimated on the assumption that
a physical I/O (Driver Call minus Cache Hit) is 2.0 times as
CPU-costly as a Cache Hit. You can change this assumption by
specifying the TPRODUCE <option> 'IOFACTOR <value>' when you
run this query. The default value for IOFACTOR is 2.0, the
same default as is used by the Tandem Capacity Model (TCM).