Explanation of Confidence field being shown on Tivoli Performance Analyzer panel

The Tivoli Performance Analyzer calculates amongst other things - something called Confidence of data during the course of it's computation.

Data for the TPA (Tivoli Performance Analyzer) is gathered from the Tivoli Data Warehouse and here I will write about how the Confidence value shows up on the TEPS GUI when looking at CPU Utilization for Linux OS Agent.

Confidence is the measure of how well the data being calculated is close to each other.

To begin with, the definition

The status output attributes are:
Confidence
Calculates the correlation co-efficient and multiplies it by 100 (R2 * 100) to give
an indication of how accurate the approximated trended value is. This
calculation is a product of the Least Squares Regression method and creates a
number between 0 and 100 where 0 is no confidence and 100 is a perfectly
approximated function. The number gives you a level of confidence in the
trended value calculated, and can help reduce the number of false positives in
situations.

More information can be found at :
http://publib.boulder.ibm.com/infocenter/tivihelp/v15r1/index.jsp?topic=%2Fcom.ibm.itm.doc_6.2.3fp1%2Fitpa%2Fitm_pauser.htm

Let's look at an example where I will discuss about the "CPU Utilization " on the Linux OS Agent.

If the data ( i.e AVG_CPU_Usage_Moving_Average column) in   itmuser."Linux_CPU_Averages" table is consistent- then  we can expect a good confidence level

i.e 100 %

Here I have data for 21 days and the CPU is consistently showing a 100% usage - then  it means the confidence level is high. so I' m 100% confident that the CPU Usage was pegged high all the time.





If I peeked into the TDW database, this is what I found.

AVG_CPU_Usage_Moving_Average
---------------------------------
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00
                           100.00

  21 record(s) selected.


--

Second scenario:

Next, Let's say the CPU was pegged at  35% all the time ?

Here too - I can find that the confidence will be high, since I have seen a good consistency.






AVG_CPU_Usage_Moving_Average
---------------------------------
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00
                            35.00

  21 record(s) selected.

--

3rd scenario:

Lets say I have varying CPU Usage then the confidence drops - as they are not consistent ( or close to each other )

( same samples count, i.e 21 days )







And the backend TDW  is showing that the data is varying ( or not around each other )

AVG_CPU_Usage_Moving_Average
---------------------------------
                            91.83
                            88.25
                            93.95
                            95.57
                            93.18
                            94.44
                            94.07
                            86.73
                            94.92
                            84.38
                            91.34
                            89.53
                            86.69
                            88.48
                            85.30
                            87.13
                            91.86
                            93.69
                            89.88
                            91.66
                            92.33

  21 record(s) selected.


Hope this small tutorial helped you when you are looking at the confidence being rendered on the TEPS GUI.