yes thanks. Found some intressting thread.
Answers exactly my problem:
https://community.openhab.org/t/data-loss-after-uncontrolled-reboot-for-several-days/137760/5
It is not possible to prevent the openhab system to all failures. So in fact it can happen that the system interrupts. (btw.: its happen to me). So with ZRAM enabled the data is always lost because it isnt a clean reboot/shutdown. Thats really bad. I though like the other thread creator that zram stores the data from time to time on the disk and not always in ram.
Now i didnt use zram and save the data not on every change.