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You should read the introduction at the [Log4net website](🔗) for a better understanding before reading this topic.

When you deploy the _EPiServer.Logging.Log4Net_ package in your solution, any logging by the system uses the `log4net` framework.

## Logging levels

The following levels of logging are assigned according to **priority** level, with **OFF** having the highest value and **ALL** the lowest value:

  1. OFF

  2. FATAL

  3. ERROR

  4. WARN

  5. INFO

  6. DEBUG

  7. ALL

## Enable logging

You control logging from _EPiServerLog.config_. Place it in the same directory as the application’s _web.config_ file. The logging configuration is separated from _web.config_ in case you want to enable logging when the application has entered a bad state and you have to change and save the configuration file. If the information is in _web.config_, the web application is restarted when you save _web.config_, possibly clearing the cause for the problem that you wanted to log. Keeping the log configuration separate from _web.config_ eliminates this problem.

A very simple log configuration file may look like this:

If you want to enable full logging, simply change the level value in the root tag to **ALL**; this gives you a lot of data.

## Disable logging

You have the following ways to disable active logging:

  • Set the level to **OFF** in _EPiServerLog.config_.

  • Remove the file and restart the website by saving the system settings/_web.config_ again, killing the process, or resetting IIS. It is not enough to just remove the file because the website must be restarted to disable logging.

## Log site information

The site information is primarily concerned with logging various problems and unusual events. Basically you should always monitor events with log level **WARN** and above. Events with lower levels are primarily intended to get information to track down specific errors and/or bugs. You can enable full logging to a `RollingFileAppender` in the development environment to check what has happened in Optimizely Content Management System (CMS) if a specific problem occurs (see the log4net documentation). However, during regular production use, you would probably want to just monitor WARN events and higher.

**Exceptions** are logged with the complete stack trace to let you track down exception errors. Be aware that exceptions are expensive in terms of performance. Avoid writing code that generates exceptions as part of the normal program flow.

## Organize log file storage

For a production site, you must have a policy regarding log files to avoid problems, such as exposing log files on your website, filling up a system partition with log data, and so on. The CMS logging functions monitor the health of your Web application and should not (under normal operation) cause excessive logging, as long as you do not enable logging of events below the WARN level.


If you are using remoting, UDP appenders or any type of appender that does not write log files to the local drives, the actual storage of log data will probably not happen on the Web server, although other restrictions may apply.

CMS recommends the following ways to store log files. You must have at least write permission for the directory that you wish to log to for the account that you are using for your website.

  • Store log files **outside** the folder structure exposed by the web server. This means that if your CMS application is installed in the _C:\\EPiServer\\EPiServerSite1_ folder, **do not** store your log files in the \_C:\\EPiServer\\EPiServerSite1\\App\_Data_folder (default storage). Depending on web server configuration and file access rights, this could expose your logs to any visitor to your website.

  • **Do not** store log files on the system partition. This means that if your web server has the operating system installed on the _C:_ drive, store the log files on another drive. Even though CMS’s log functions should not cause large log files during normal operation, the log files may grow very large if you enable full debugging. If the logging takes all free space on your system partition, you will experience problems, most likely making your website unavailable until the situation is resolved.