How Spms Index Values Are Calculated; Basic Indices; Aggregate Indices; Calculating Basic Indices - Nortel DMS-100 Series Application Manual

How SPMS index values are calculated

SPMS calculates switch performance by using two kinds of index: basic and
aggregate.

Basic indices

A basic index consists of an operational measurement (OM) and a weighting
factor. The factor is a calculation that uses constants derived from field
results for a broad sample of offices so that index results are relative to this
sample. The calibration of the indices take into account Automatic Trunk
Testing (ATT) and other routine system diagnostics.

Aggregate indices

From basic indices, aggregate indices are calculated as a level higher up the
hierarchy. Each aggregate index is a weighted average of its basic indices.

Calculating basic indices

The calculation of each basic index uses three constants. The values of these
constants are shown on SPMS output, in the columns headed R95 and R80.
For example, the output for a particular index might appear as:
..INDEX
In this example, the B and the data under the R95 and R80 headings indicate
that INDEX is a basic index. The R95 value is 27, the scale factor is
1,000,000 (10 to the power 6) and the R80 value is 216.
SPMS starts the calculation by dividing the measured value by the
normalizing factor and multiplying by the scale factor. The scale factor is
used to make the normalized result a whole number rather than a fraction
(example: errors per 10,000 calls rather than ten thousandths of an error per
call). The scale factor is chosen to make the predicted result of scaling fall
within the range from 26 to 255. The result is called the scaled normalized
ratio, or R for short.
DMS-100 Family Switch Performance Monitoring System Application Guide BASE09 and up
L WT R95 R80
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B 30 27 6 216
9-1