# Backlog

Backlog is designed to prevent data disappearance in the event of long-term loss of communication with the target store. This is achieved by saving data to the local disk and writing it again after the connection is restored. The backlog mechanism is available for all store types and offers the following settings:

* **Mode**: specifies backlog mode (*None* – do not use backlog, *Cyclic* – write files to disk cyclically).
* **File Size:** specifies the maximum backlog file size (in KB) that can be saved for each time series.
* **Files Count**: specifies the maximum number of files that can be saved for each time series. When this value is reached, the files are cyclically overwritten.
* **Buffer Size**: specifies the number of samples at which the backlog file is flushed to disk.
* **Flush Interval**: specifies the interval (in seconds) after which the backlog file is flushed to disk.

By default, the backlog is saved in the following directories:

* **Windows**: %ProgramData%\Monokot\Mos\Backlog\ (C:\ProgramData\Monokot\Mos\Backlog)
* **Linux**: /usr/share/Monokot/Mos/Backlog/

{% hint style="info" %}
Please note that these directories are hidden file system directories
{% endhint %}

You can change the backlog directory in the server [<mark style="color:blue;">startup settings</mark>](/basics/startup-parameters.md).


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