Database or disk is full when saving project

Hello,

when I save my Ignition project I run in this error:

"GatewayException: java.sql.SQLException: database or disk is full
caused by SException$Jdbc: java.sql.SQLException: database or disk is full

Ignition v7.9.4 (b2017082911)
Java: Oracle Corporation 1.8.0_201"

The internal database is only 4MB, but I cannot save any modification.
I tried to backup and restore it, but with no succes
Any idea on how to solve this problem?

Thank you
Andrea