OR Your Systems manager's declarations:
-"Y our software has started PageFaulting like mad"
- Adding memory improved response time"

             figure 2
Your system-manager's declaration

OR Your whiz-kid programmer boasting:
-"/( is tenfold faster"

            Figure 3
Your wiz kid programer boasting

 OR At times, you enter into a contract specifying
 what the response time should be. The contract is
 based on a business transaction basis, e.g.,
-"Finish 95% of the update-transactions within ten
seconds in 97% of the days".
 Did you fulfil the contract?
 OR take your own question :
 - "Does the system behave differently now, then
previously?"
To satisfy yourself and your clients that you have

fulfilled the terms of the contract you have to take into
consideration changes of work load between days,
changes in transaction mix and interaction of different
systems.Your ability to objectively check these claims
regarding response time, in a way that will be under-
stood and accepted by your clients, is a key element of
trouble shooting, never ending improvement, pride of
workmanship, software evaluation and industrial peace.

   Management must measure performance objectively
   and draw conclusions from the collected data. Measur-
  able parameters in the implementation stage in a
  system's life cycle are, for example, number of errors
  per function unit, delivery dates and budget. At the
  maintenance stage in a system's life-cycle response
  time is the parameter that should be managed, as
  response time is victim of the most frequent com-
  plaints, sensitive to software errors, an indicator of
  high consumption of other resources, sensitive to inef-
  ficient code and to demand fluctuation. PTA investi-
  gated the programs whose response time were worst
  during a hundred business days. PTA found that these
  programs were also the biggest CPU time, direct VO
  and buffered I/O consumers.
  Managing response time constrains never ending
  improvement on ISD, rather than meeting specifica-
  tions that are set in concrete. PTA, thus, relates
 response time to quality of clients service and evalu-
 ates its service with the help of Statistical Process
 Control (SPC), implemented using DECtrace for VMS
 (Icnown by the acronym - 'EPC') as its data collector.
 PTA defined a number of business transactions of
 special interest ('event' in EPC terminology) such as
 Trade', 'Reversal' and 'Cheque Print'. EPC routine calls
 were placed, first, in the most frequently used pro-
 grams. Later, during maintenance, EPC   service
 routines calls were placed in the rest of the programs.
 The method of calling EPC service routines from a
 program is described in part 4 of this paper. The
 method of analysing the collected data and presenting
 them is described in part 5 of this paper.
 With its own accumulated experience, PTA learned
how to interpret and use the results. Currently, every
change in the environment is evaluated on the basis of
response time reports ("Yes, it is faster now" or: "The
added functionality is worth the slower response
time"). Three case studies, at the end of part 6 of this
paper,  will  demonstrate  real  life  usage  of this
technology.

103