LYONNAISE DES EAUX: active redundancy

The centralised control of the Lyonnaise des Eaux at Le Pecq (Operational Centre of the Yvelines region) manages approximately 5000 variables from 6 production plants and 41 network management stations. The previous supervision system, installed in 1989, offered under VAX VMS manually shifted redundancy functions, but resulted in heavy maintenance. The SIT, Service d'Informatique Technique (Technical Computing Department) wished to turn to a solution based on TOPKAPI by studying precisely the requirements together with AREAL, because this application had to be the first within the Lyonnaise group implementing active redundancy on PC with hot switching. After a few work meetings, the following system architecture was decided upon:

Stations 1(primary) and 2(secondary) acquire and process the data, via two SDG redundant data servers developed by the CITI. During normal operation, station 2 behaves as a client of station 1; this means that two operating stations are available without multiplying the number of stations (servers and operating stations). Station 3 is dedicated to alarms and switches automatically its communication to the secondary station should the primary station fail; data unicity enables to perform acknowledgements from any network station

The application was developed by the SIT and tested as a single station application, then the redundancy itself was implemented in half a day with the help from an AREAL engineer, plus half a day users’ training. Finally, the application was started one month before the set deadline. In its current PC configuration, the system enabled to divide by 3 the response times to commands when compared with the VAX VMS system. The maintenance costs have been dramatically reduced, as the operators using the operating station fully master TOPKAPI and enhance the application during their operating time; these modifications match accurately coded procedures in order to prevent that, as it is unfortunately often the case with other applications, they would make the application cumbersome and inconsistent in the mid term.