Virtual DataPort uses the root file appender FILEOUT which logs to the vdp.log file. By going through the log **An exception occurred processing Appender FILEOUT** error occur when you have made any changes in the conf directory regarding one of the **log4j.xml** files file pattern, and maybe logging for the error is broken. So, please ensure that you have made any changes in the log file pattern. By default VDP log are generated in the file pattern as similar **vdp.log.0**.
In addition to that, if you are Denodo Support User then I would recommend you to raise a new Support Case with detailed information at the [Denodo Support Team](https://support.denodo.com/), so this particular behavior could be reviewed by the Support Team and help you to resolve this issue.
Hope this helps!