It is important to note there is a correlation between all the parameters
Memory limits must satisfy:
static_min ≤ dynamic_min = dynamic_max = static_max
To modify the memory configuration for a Virtual machine in XEN through the cli commands you will have to stop the server
# xe vm-shutdown name-label="machine name"
Review the current memory configuration with
# xe vm-list params=all name-label="machine name" | grep memory
you have to find the uuid of the machine, that can be showed listing the uuid by
# xe vm-list params=uuid name-label="WINS Nameserver"
Change the memory configuration with
# xe vm-param-set memory-static-max=668435456 memory-dynamic-max=668435456 memory-dynamic-min=668435456 uuid=ffffb8a9-ffff-ffff-2df1-fffc9bd9688a
Start again the machine
# xe vm-start name-label="machine name"