The reason for this could be that you use the scheme command “pick” to extract certain output of a text command somewhere in your setup. Currently, every call of “pick” (or a related scheme command like “pick-hard”, “pick-robust”, “pick-a-real”, etc.) leads to the creation of a text file in the temporary directory of your system. The file might be empty or contain the output of the text command for which “pick” is called, depending on the specific version of “pick” you are using. The files are not cleaned up after the simulation run and thus could fill up the temp-directory after some time. This behavior will be corrected in version 2019 R3. Meanwhile, if you need to use “pick” but want to get rid of the files that it creates, you can identify the pattern that is used for the files and include a system command which periodically removes the generated files using the “Execute Command” feature. On many Linux systems, the file name is “file??????”, where each ? stands for a random letter or digit, for example “fileA4cx9Z”. When you use the standard temporary directory /tmp, then the command would look like this: (system “rm -f /tmp/file??????”) On Windows, the corresponding command for the same file name pattern would look like this: (system “del /f %tmp%file??????”) Please be aware that on some systems, the file names do not have the prefix “file”, but just consist of a number of random digits/letters, so you would need to remove, e.g., “??????” instead which is quite risky – you might want to clean up the temporary directory manually in these cases instead of using the automatic removal procedure as described above.