100% CPU using LabView 7.1 and DSC module

[AJmex]

Seven years ago I used BridgeView and PXI to execute a project, and the results were so good that after that initial system, I installed one more using BridgeView, and three more using LabView 7.1.

BridgeView is working very well, but lately, LabView 7.1 is giving me more and more problems. It all started in a system running LabView 7.1 and DSC on Windows XP, using a PXI-8187 controller with a PXI-1042 chassis. I have two PXI-6533 digital I/O boards, one PXI-6030E multifunction, one PXI-6713 analog output board, one PXI-6602 counter board and one PXI-8422 serial com. board. In may/06, all of the sudden, the CPU went to a 100% use. Since I am running PID's to control a flash-butt welding machine in a steel factory, this was extremely dangerous. I changed the controller and everything went back to normal. It was running fine until december/06, when the same behavior appeared again. This time changing the controller did not help. We increased the system memory, from 256 MB to 512 MB and everything worked fine. But one month later (january/07) the fault reappeared. This time we changed the chassis and from that moment to this time, we are running smoothly.

Application problems were suspect from the very first time this problem appeared, but I was unable to identify the source, if any. I used PROFILE VI's and apparently the write/read tags were taking all the processor resources. However, changing the routines and disabling communications, and optimizing CPU intensive programs never solved the CPU overload.

Until now, I was aware of only one system showing this erratic behavior. But today I went to check another system, with a totally different application. This one is used to measure the thickness of the steel sheet on a rolling mill. Is not so resource-intensive, but the maintenance folks told me that every time they turned off this particular system, they always had problems trying to turn it on.

I was suspecting of a PLC-communication related issue, but what I found turned my alarms on. I turned off the system, which was fully functional, and turned it back on, and there it was, CPU load at 100%!. Is exactly the same problem that I have on the welder. This system has a PXI-8184, a PXI-1042 chassis, Windows XP, one PXI-6030E, one PXI-6713 and one PXI-6533. I battled for 20 minutes to put the system back in normal conditions.

I specified every single board, installed everything and programmed all the applications. The BridgeView applications have never showed anything like this. I am using the DSC (Datalogging and Supervisory Control Module) on both applications, and the Lookout Protocol Drivers are communicating to Modicon PLC's.

Please, I need help to solve this issue. I believe none of your actual Knowledge Base "100% CPU" articles apply to my case...

Thanks in advance...

Antonio Jimenez

jajimenez@terniumhylsa.com

[unclebump]

Are you saving data to the citadel database?? How long is the data being stored?? Maybe change it to a new location to start a new database file.

[AJmex]

Thanks for your reply...

Yes, sometimes I have the feeling that the systems works again because some file or database gets initialized after so many reboots.

Intentionally I turned off all the events and alarm logging to disk. Also the historical data logging is disabled. This is done by code, every time the main VI is started. This was included precisely to save CPU processing power. However, I am communicating to PLC's, and of course I have to declare variables inside the citadel database to make the communication possible.

Right now I can't have access to the application, because the mill is rolling, but during the next maintenance stop I will check the database location and size, and I could change the directory location the next time the fault comes up.