Not enough memory

Hello,

I have no backup of my virtual machines for 5 days. I restart Acronis Appliance and try to understand why. In the event log, here are the errors I found.

Memoire insuffisante.
Informations additionnelles :
--------------------
Code d'erreurs : 2
Module : 0
LineInfo : 2fb3f755326e0784
Champs :
Message : Memoire insuffisante.

Where does this problem? How can I avoid this problem in the future ?

Thanks