Shell Programming and Scripting

I receive on a daily basis CPU measures on a UNIX Server (AIX 5.3 version, korn shell). These CPU measures are provided by Omnivision tool.

We could see that Omnivision daily stats are not always equal to NMON stats regarding CPU level.

On my side (I work in an IT Production Support Team, not on UNIX System team), I've activated a CPU daily monitoring with sar command.

By default, sar CPU measures are provided every 5 minutes

Code:

/home/l479029 ) sar

AIX parva1006052 3 5 00C9053E4C00    07/15/11

System configuration: lcpu=10 ent=2.50 mode=Uncapped

00:00:00    %usr    %sys    %wio   %idle   physc   %entc
00:05:01      37      10       0      54    1.29    51.4
00:10:00      29       8       0      63    1.04    41.8
00:15:00      26       8       0      66    0.96    38.5
00:20:00      30       8       0      62    1.06    42.3
00:25:01      31       8       0      61    1.11    44.2
00:30:01      30       8       0      62    1.06    42.4
00:35:00      29       9       0      61    1.09    43.5
00:40:00      28       8       0      64    1.01    40.3
00:45:00      30       9       0      61    1.09    43.7
00:50:01      31       8       0      61    1.10    44.0
00:55:01      30       8       0      61    1.09    43.7
01:00:00      22       7       0      71    0.83    33.2
01:05:00      38      23       0      39    1.66    66.4

Regarding average CPU levels or CPU peaks, CPU measures which are provided by sar tool are always more "optimistic" (I mean with less CPU consumption level) than Omnivision CPU measures.

I imagine that the gap between both tools is linked to measure frequency, as CPU level on an UNIX Server is a very volatile data.

I tried to setup sar for more frequent measures rather than default 5 minutes frequency.
However, when I execute following command sar 5 17280 on a test server, I do not get all day history since midnight, as it is reported with default sar execution.

How can I both increase frequency of CPU measures with sar to make it more reliable and consistent with Omnivision, and also keep all reporting from 0:00 to 23:59 (the target afterwards for me is to calculate the CPU daily peak and the 24 hourly average CPU levels for each day) ?

Furthermore, between sar and Omnivision, are there technical gaps for CPU measure (for an equal frequency measure) ?

Thanks by advance for your help.