Fundamentals of Capacity Management (Part IV)
Article 4/99
Tuning the Operation
Last time we saw the table below which covers a full day (by half-hour, edited). I suggested that there might be opportunities herein.
|
tps |
cp/tps |
cpu |
dk/tps |
disk |
trans |
| '02:00 Mo 10/26/98' |
0.4 |
38.0 |
13.8 |
92.8 |
33.7 |
654 |
| '06:00 Mo 10/26/98' |
6.3 |
3.3 |
21.0 |
9.0 |
56.3 |
11310 |
| '11:00 Mo 10/26/98' |
10.6 |
2.1 |
21.7 |
3.6 |
38.6 |
19053 |
| '11:30 Mo 10/26/98' |
10.7 |
1.9 |
20.8 |
3.5 |
37.1 |
19301 |
| '12:00 Mo 10/26/98' |
11.4 |
3.8 |
43.5 |
14.8 |
169.3 |
20540 |
| '13:00 Mo 10/26/98' |
10.9 |
2.4 |
25.8 |
9.4 |
102 |
19554 |
| '13:30 Mo 10/26/98' |
10.7 |
4.5 |
48.4 |
60.8 |
648.3 |
19193 |
| '14:00 Mo 10/26/98' |
11.0 |
2.2 |
23.8 |
4.1 |
45.2 |
19838 |
| '17:30 Mo 10/26/98' |
14.6 |
1.8 |
25.9 |
3.1 |
45.5 |
26349 |
| '18:00 Mo 10/26/98' |
13.4 |
3.3 |
44.2 |
13.1 |
175.5 |
24077 |
| '18:30 Mo 10/26/98' |
11.1 |
2.5 |
28.3 |
6.6 |
72.8 |
20002 |
| '21:30 Mo 10/26/98' |
4.3 |
2.9 |
12.7 |
4.9 |
21.3 |
7807 |
| '22:00 Mo 10/26/98' |
3.3 |
8.4 |
28.0 |
29.0 |
96.8 |
6012 |
If we look closely at the table, some things are evident:
- In the best of all conditions, it only takes about 1.8% of the computer to process 1 TPS. Based purely on this number, the CPU is capable of performing 40-50 TPS. Note, though, that CPU is only one of many factors to be considered. You will also have to look at disk busy, comm throughput, process threads, and other items since each is a potential bottleneck in the system. Realize that there is always a "next" bottleneck. You simply may not have hit it yet.
- There is some heavy background processing going on at 02:00, noon, 13:30, and 18:00. All of these times show heavier than usual CPU and (especially) disk activity. This is the opportunity I mentioned above. If there is any way to reschedule (or eliminate) this processing away from the peak transaction times you should do so. Sometimes this can't be done, since your processing may be imposed from the outside, such as by bank reporting cutoff times.
- Also, take a second look at those heavy background processing times. Are all of them required jobs? Is there some unexpected developer or operator activity going on that can be eliminated? We occasionally find operators running unauthorized macros which, while the operator's intentions are good, cause enough load on the system to affect operations.
One last thing: As you investigate the background activity, be sure to verify the priority and quantum that each job is using. It's not uncommon, especially if your site is using the default VOS scheduler, for batch or background jobs to be running at the same or higher quantum than the online transaction processing system. If so, fix the scheduler and/or fix the priority of the jobs.
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