Problem min and max since?

[Dim (Angelos)]

@paulmann

but i dont know what this is

You mean that you don’t know what is the rrd4j persistence service?

If yes: Check http://docs.openhab.org/configuration/persistence.html. Follow the link to the OH1 Wiki
(or rrd4j Persistence · openhab/openhab1-addons Wiki · GitHub)

Basically: A Persistence service stores historical information about the state of your items in a database.
Read more about this on:

Design Pattern: Group Based Persistence

Edit: Updated for OH 4 See Design Pattern: What is a Design Pattern and How Do I Use Them for an explanation of what a DP is and how to use them. Problem Statement There are several reasons why a home automation enthusiast would want to use openHAB persistence: charting, using historical Item states in rules logic, restore previous values on openHAB restart, detailed analysis, access to the data with external tools, etc. By default, a persistence add-on will implement a default strategy which…