FUJ00142152
FUJ00142152
Problem with BTS Stock Levels
Ref: __r:\hng plan x\architecture\end to end assurance\btsstocklevels.doc
Author: Gareth I Jenkins and Jon Hulme
Date: 12/02/2010 15:53:00
1. Introduction
Yesterday, Peak 194458 was raised from Warwick Post Office (506246) about
incorrect Stock Figures on their Branch Trading Statement (BTS).
The purpose of this note is to explain the problem and the underlying cause and
proposed fix.
2. The Problem
Firstly it is worth explaining what the BTS is.
It is a report produced at the end of a Trading Period (TP) providing a summary to the
Postmaster about the trading that was done during that period. When the report is
produced the Branch is moved (or Rolled Over) into the next TP. The report can only
be produced when all the Stock Units have rolled over into the new TP and certain
mandatory Branch level reports have been produced. It is normally produced every 4
or 5 weeks either on a Wednesday evening or a Thursday morning. Problems in
producing the BTS do not prevent the Branch from continuing to trade normally.
During BTS production the report is produced twice:
= A Trial Report to allow the Postmaster to check that the data is correct
= A Final Report which is produced after the trial report has been confirmed. This
indicates that the Branch has rolled over into the next TP.
The BTS consists of two parts:
= Summary of Stock Unit and Suspense Account activities over the Trading Period
= Consolidated Branch Stock levels for all Volume Stock items
There have been issues (originally found at Coton and Warwick) with the figures in
the first part of the report. Development took a copy of the data from Warwick on
Thursday 12 Feb and checked that these figures in this part of the Report were
correct.
However this Peak relates to the second part of the report which shows the
consolidated Stock levels.
The problem is that in the Final Report, many of the figures are incorrect.
It should be noted that:
a The figures on the Trial Report (which the postmaster is asked to check) are
correct
a The figures that are stored as Opening Figures for the new Trading Period are also
correct
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FUJ00142152
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The only thing that is incorrect is the printing of figures on the Final BTS.
Development did not check this second part of the final BTS as there had been no
previously reported problems with this, and no reported differences between the trial
and final reports. Even when the second part is examined, the error is not obvious as
demonstrated by the fact that several branches have balanced and not noticed, when
they were highly likely to have had this error.
3. The Cause
The root cause of the problem is that the code that re-prints the report manages to
overwrite some of the cache of data held at the counter for generating the report as it
is printing the report.
4. The Fix
The fix is to ensure the Trial and Final reports work on copies of the cached data
which are discarded when the report completes, thus ensuring that any changes made
to the data during the production of the report have no impact after the report
completes.
This is a one line change to a velocity template, which a held as Development
Reference Data. This still needs to be developed and tested through the development
process.
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