Client:          Sparekassernes Data Center,  Copenhagen

Project:         High Performance Transaction Message Switch

Dates:            Jan 86 /  Mar 87

Team Leader










OSI Communications
Message Switching
























Data Flow 

Testing



IBM Assembler Programming




Performance Tester 

Worked for 15 months as a Team Leader on a large project at the Sparekassernes Data Center near Copenhagen, building, integrating and testing a high throughput OSI/SNA based banking transaction message switch on an IBM 3084 mainframe under MVS/XA. The message switch was one of the components of a large network that included over 1300 Olivetti mini-computers situated in savings banks throughout Denmark and Greenland. These were connected, via the Danish PTT's X.21 switching network, into 7 IBM 3725 communications processors at the data centre.

The switch being implemented, used standard SNA/VTAM sessions to interface these 3725's to a host IBM 3084Q/3090 which ran the on-line banking transactions system. The switch itself was based on modified OSI Transport and Session protocols and running both high & low volume data streams.  Each Local Computer opened a 'Path' to the Message Switch, over which it would then establish ,p to 30 'Associations'.  These associations could run various type of data streams, passing data as Letter Fragments.  One such data stream was for high volume, low. content, data consisting of single fragment unacknowledged Letters (STP protocol).  An other data stream was for lower volume, high content data consisting of multiple fragment acknowledged letters (SEP Protocol). This second protocol implemented a pseudo OSI Class 4 Transport Layer and included transmission/receive windowing, flow control, Letter fragmentation, and re-assembly, re-sequencing, fragment retransmission and acknowledgement The switch could handle over 30,000 concurrent data streams with an averaged throughput of 300 message pairs per second.

During the development phase, was personally responsible as  a Team leader, supervising 6 programmers during the coding of some 200 separate software modules.  During the build & integration phase, was team leader supervising 3 programmers. These two phases overlapped for a period when both teams were being supervised at the same time

Was responsible for researching and defining the switch's error handling methodology. Initiated and maintained a fault reporting system and quality assurance system, ensuring that any updates/fixes were always tracked and reflected accurately within the technical specification.

Responsible for the control and administration all software comprising the switch.  Responsible for generating Unit Test scripts against which the programmers verified their completed modules.

Responsible for updating pseudo code in the technical specification to reflect coding changes to some 70 assembler/PL1 modules.

Generated and ran some of the  TPNS message decks to perform data validation tests on the message switch.

Coded and tested some of the fixes for the various Assembler and PL/1 programming faults. During the system testing phase, performed assembly language code enhancements and restructuring to a in-house developed, assembly language,  performance testing tool. The tools was designed to initiate multiple SNA sessions with the switch and simulate high volume data traffic. Personally enhanced this to use multiple virtual transmission routes between source and destination CPUs,  to provide  recovery from SNA/VTAM error conditions, to allow automatic recovery from session outages and to impose inactivity checking for all established sessions. Responsible for the setting up and running of performance acceptance  tests which used this tools.