Citrix retired the Virtual Machine Protection and Recovery (VMPR) in XenServer 6.2. VMPR was the method of backing up snapshots as Virtual Appliances.
Alternative backup products are available from Quadric Software, SEP, and PHD Virtual
With XenServer 6, VM Protection and Recovery (VMPR) became available for Advanced, Enterprise and Platinum Edition customers.
XenServer 5.6 SP1 introduced a basic XenCenter-based backup and restore facility, the VM Protection and Recovery (VMPR) which provides a simple backup and restore utility for your
critical vims. Regular scheduled snapshots are taken automatically and can be used to restore VMs in case of disaster. Scheduled snapshots can also be automatically archived to a remote CIFS or NFS share, providing an additional level of security.
Additionally the Citrix Hypervisor API allows for scripting of snapshots. You can also (manually or script) export and import virtual machines for backup purposes.