> For the complete documentation index, see [llms.txt](https://support.powerio.com/hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://support.powerio.com/hub/faq/faq-en/hvac-codesys-faq/codesys-log-und-exception-log-sichern.md).
# Backing up the CODESYS log and exception log
This is how you back up the CODESYS log and the exception log of the OnException function after an exception via the Files tab in CODESYS.
After an exception, back up two files: the CODESYS log `codesyscontrol.log` and the exception log `codesysexception.log`. Both files are loaded into CODESYS via the tab **Files** onto the PC. The exception log is created only if the function `OnException` uses the relative path `codesysexception.log` .
Prerequisite: CODESYS is connected to the device.
## Download CODESYS log
1. Open the device in the device tree with a double-click and select the tab **Files**.
2. Click in the **Runtime System** on **Refresh**.
3. Select `codesyscontrol.log`. Also select `codesyscontrol_0.log`, `codesyscontrol_1.log` and `codesyscontrol_2.log`, if present.
4. Click on **<<**. CODESYS copies the files into the folder that is open in the **Host** area.
The runtime overwrites the oldest entries as soon as the log reaches about 4 MB. Therefore, back up the CODESYS log directly after an exception.
If `codesyscontrol.log` is missing, the log is located on the device in a place that CODESYS does not display. The cause and the solution are under [Where is the CODESYS log located on powerIO devices?](/hub/faq/faq-en/hvac-codesys-faq/wo-liegt-das-codesys-log.md).
## Set up exception log
The exception log writes a line with task and exception code for each exception. The CODESYS log does not contain an entry for the exception after an automatic restart.
1. Open **Task configuration** > **System events**. Check that the event **Exception** calls the function `OnExceptionWrapper` and is active.
2. Open in the view **POUs** calls the function `OnExceptionWrapper`. Check that the call `xLogExceptionToFile := TRUE` contains:
```iecst
OnException(EventPrm := EventPrm, xDebug := FALSE, xLogExceptionToFile := TRUE, xRestartRuntimeOnException := TRUE, tExceptionFunctionTimeout := T#45S);
```
3. Open the function `OnException`. Replace in `sExceptionLogPath` the path `/tmp/codesysexception.log` with `codesysexception.log`.
4. Upload the project to the device.
The runtime blocks paths outside the folder `PlcLogic`. With the old path, no file is therefore created, and the CODESYS log shows `Access denied to '/tmp/codesysexception.log' due to ForceIecFilePath`.
## Download exception log
1. Open in the tab **Files** in the area **Runtime System** the folder `PlcLogic`.
2. Select `codesysexception.log` and click on **<<**.
Each exception results in one line:
| Field | Meaning |
| --------------- | ----------------------------------------------------------------------------------- |
| `Timestamp` | Time of the exception in milliseconds since 1 January 1970, already in local time |
| `Task` | Task in which the exception occurred |
| `ExceptionCode` | Type of exception, for example `81` for a memory access violation |
| `Action` | Reaction of the function, for example `TryExternalScript` for the automatic restart |
---
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