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Problem with WinCC C-Script running slow but only first time

Created by: jayr at: 5/12/2008 3:56 PM (12 Replies)

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5/12/2008 3:56 PM	Rate (0)
jayr Posts: 7 Rating: (0)	I have several C-Scripts that involve reading and writing to text files. They run perfectly except for the first time they are run after starting runtime - in that case they are extremely slow. For example a script that normally runs in less than one second takes sometimes 6 minutes the first time. I am running Win XP and WinCC 6.2, HF9 Thanks for your help
jayr Posts: 7 Rating: (0)
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5/13/2008 9:45 AM	Rate (0)
April Posts: 1776 Rating: (95)	Hi, have you checked your diagnostic files? Run the Apdiag during starting WinCC runtime. Use printf in the scripts running slow, to see which part of the script takes long time. Maybe the communication between WinCC and the controllers takes time to start. just see the FAQs for helpful diagnostics http://support.automation.siemens.com/WW/view/en/22892165
April Posts: 1776 Rating: (95)
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5/13/2008 2:49 PM	Rate (0)
jayr Posts: 7 Rating: (0)	Hi April, I have looked at the diagnostic files and run apdiag with printf notifications as well. Nothing jumps out at me. The scripts are basically reading tags (floats, strings, words) and writing or them to a file. When I watch the progress in apdiag there is no particular point in the script that is slow, the whole thing seems to be - but I believe it is reading the tag that is slow, not writing to the text file. Once it runs once it is then fine. In fact I run it every minute and it takes less than 1 second each time. It doesn't matter if WinCC has been running for an hour - the first time is always slow.
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5/14/2008 12:17 PM	Rate (0)
Steffl Posts: 19 Rating: (0)	Hi jayr, i have the same Problem with a GlobalVBA Script!! I contacted the wincc hotline and they told me, that on first WinCC Tag reading the Tag will be puted into a process image. When the Taghave been putedinto theProcess image it can be read very quickly!! So i think you can do nothing to solve this problem!! ...SteIns
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5/14/2008 3:34 PM	Rate (0)
jayr Posts: 7 Rating: (0)	Thank you for your information. That definately sounds like what I am seeing. I wonder if any of the experts can advise a work around or a solution? Thanks, Jay
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5/14/2008 10:22 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 12/9/2025 Posts: 2957 Rating: (243)	Hi, What connections driver do you use for your tags ? I used modbus OPC server and that first time of script was slow like hell. I had 150 tags and it took about 10 mins for first run. There are two posibilities: you may use normal GetTag... functions and get slow first time of scripts or you can allways use GetTag..Wait functions which will be allways slow becouse they don't read tags from image, but read them directly. Actually there is no workaround. In my case the workaround is change modbus OPC server to normal ethernet communications. I had a project with >10k tags and they all was on ethernet and didn't noticed any slowdown. So just check what comm driver do you use and what speed. I think ethernet will solve problem. If you allready use ethernet so I think problem is somewhere else becouse ethernet speed is very high and your script will read tags to image very fast. Sorry if my post is a little messy Regards, Darius
	Best regards, Darius
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5/15/2008 4:10 PM	Rate (0)
jayr Posts: 7 Rating: (0)	Thank you for your info and advice. I am running Siemens S7 Ethernet comms to a S7-317 - I would assume this should be fast.
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5/15/2008 4:30 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 12/9/2025 Posts: 2957 Rating: (243)	Hi, So I think this is the problem, becouse ethernet comms can't be so slow. You shouldn't notice it. So I think you need to try to find other solution for your problem. Here I have no ideas left. Good luck. Regards, Darius
	Best regards, Darius
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5/19/2008 4:30 AM	Rate (1)
RonaldNijssen Experienced Member Joined: 1/21/2008 Last visit: 1/2/2026 Posts: 39 Rating: (14)	Jayr, As discussed in the thread, the issue is that the Tags you are reading need to be "announced" with the Data Manager the first time the script runs. (In other words they are not readily being read from the comm. channel) Because your script is reading these tags one-after-one, and their name is appearantly not known (as in declared in the script), each read is an individual transaction that set's up communication, each can take 300 ms, resulting in the long accumulated time. Once the tags are being read by the Data Manager, each read probably takes < 2 ms. The trick is to make something notify the Data Manager that these tags should be available and being read "before" your script runs. This can be accomplished in various ways: 1. declare them in the script and use them as a trigger 2. Put them by means of a "direct connection" in a graphic that is present before the script runs 3. Use them in tag or alarm logging A WinCC graphic solves the issue you are seeing by placing all direct connect, trigger and script tags ina "bucket" when the graphic is saved in graphics designer. When the graphic is called on the run-time screen, the complete bucket is sent to the Data Manager, allowing it to get all tags their data in < 300 ms (instead of one-by-one). Hope this helps optimizing your script, which you really should, because all other scripts will stall while this script runs the first time Ronald

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This contribution was helpful to 4 thankful Users Jasonjin cajac pu_abs Rockon

5/19/2008 6:20 PM	Rate (0)
jayr Posts: 7 Rating: (0)	Hi Ronald, Thank you very much! This helps me to understand the problem and with some workarounds it is much better. Excellent response! Jay
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