Applies To:
  • CitectSCADA 6.00
  • CitectHMI 6.00

In CitectSCADA version 6.00 the Alarm Summary length has a maximum size of 2.14 billion. Can you explain what the implications are for saving this many events and how this affects Process Analyst trending of alarms? 

Yes the limit has been increased to this size, however the default alarm summary length remains at 1000 events. You can increase the [Alarm]SummaryLength parameter in your citect.ini file to suit your project and capacity of your computers. The data contained in each summary record is stored in the alarm save file, "AlmSave.dat". The Process Analyst also displays alarm information retrieved from the alarm save file.

There is a Windows maximum file size of 4 gigabytes for FAT and 16 terabytes for NTFS but memory will be key. The entire alarm summary is stored in RAM on the alarm server. As the online Help states, 32000 events require at least 6.2 megabytes of memory so 1 million events would require about 200 megabytes.

When an alarm server starts up, the other alarm server sends all it's alarm summary records across to make sure both servers have the entire alarm summary. The transfer is quite efficient and if 2.14 billion alarm events were logged, they could all be sent to the starting alarm server. If for some reason (perhaps frequent startup and shutdown) you want to disable the copying of the alarm summary data on startup, this can be done by setting [Alarm]SumStartupCopy=0.