I have multiple parallel loops that are processing analog data (arrays of doubles) at differing rates. The loop frequency and the amount of data in each loop is different. The processes are completely independent from each other except that upon certain conditions (i.e. an exceedance, user command) each loop may need to write it's current data into a single TDMS file. Each loop's data is written into a dedicated group and and channel heiearchy. At times when more than one loop is writing to the single TDMS file, it appears that performance slows way down- by that I mean the user interface lags, queues start to fill up, loop iteration times increase. The most data I'm needing to write at any time (total) is on the order of 40MB/sec, so I doubt i'm pushing the limits of TDMS (this project is being developed on a brand new PXI chassis, with a 4 drive striped raid array), I think the problem lies in how i'm accessing the file. I'm managing the file reference in a seperate process and copying that single file reference into a local variable of each loop. Perhaps I'm going about this the wrong way? Do I need multiple file references? What's the proper way to handle simultaneous asynchrounous writes from multiple loops to a single TDMS file? Is there a good way other than splitting up the storage into seperate files?

LabVIEW

What's the best way to handle simultaneous writes to the same TDMS file?

One thing you might be able to try is to create a global function that is not reentrant. This will force the Parallel loops to wait till the VI becomes available. You can only use this if you can wait the given time to write the data to a file in each of the parallel loops, otherwise the best method is the producer/consumer method. The global function will be a more contained approach that will require the least amount of reprogramming if you already have something in place. I hope this helps some.

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