The PIVX wallet requires, at peak, more than 1GB of RAM in order to run stable.
To ensure a stabile behavior on a Raspberry Pi it is recommended to set a swapfile with 2048 MB to buffer these peaks.
Running out of RAM without having a swapfile in place will crash the wallet and could corrupt your copy of the Blockchain.
To create a swapfile on your Raspberry Pi you can use the following commands:
1) sudo su -c 'echo "CONF_SWAPSIZE=2048" > /etc/dphys-swapfile'
2) sudo dphys-swapfile setup
After creating the swapfile, you have to activate it once by using this command:
3) sudo dphys-swapfile swapon
Now your Raspberry PI has enough SWAP in place if its needed, and will not go down because of RAM overload.