> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/instrumentation/nextseq-500-550/instrumentation-nextseq-500-550-troubleshooting-list/000003878.md).

# Troubleshooting presence of snr.csv Files in Temp folder on NextSeq 500/550 (NCS 4.0.2)

Systems running NextSeq Control Software (NCS) v4.0.2 have numerous snr.csv files in the temporary run folder in D:\Illumina\NextSeq Control Software Temp.

SNR files have been introduced in the software and are expected to be present in the Temp folder. These are intended to help with signal-to-noise ratio debugging and do not get copied to the output run folder.

The local temp folders get automatically deleted by the NextSeq Control Software after a certain time period.

Example snr.csv files:

* 2021-01-11\_\_19\_07\_54\_32F03D30 GetBestZ Camera 1 Focus Red top surface.snr.csv
* 2021-01-11\_\_19\_07\_54\_32F398CF CalculateSignalStd(z\[0]=0.019553, IQData len 18, imax 9, depthOfField 0.018).snr.csv
* 2021-01-11\_\_19\_07\_54\_32F4AA19 SafeParabola called by CalculateSignalStd.snr.csv
* 2021-01-11\_\_19\_07\_54\_32F6927F SafeParabola called by FindPeakUsingParabolaFit.snr.csv

**Troubleshooting steps:**

* Leave the files in the temporary run folders as they will be automatically deleted with all remaining files and do not affect sequencing quality or time.
* There is no setting to 'switch off' the file generation.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #3878), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000003878%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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