after you have written a config file /etc/xen/abcd.cfg you have to create the instance by

xm create abcd.cfg

(It suprised me, that the suffix .cfg is neccessary)

xm console <Domain>

to disconnect type ctrl-] (which means to press Str-AltGr-9 on a german keyboard)

xm destroy <Domain>

this will not(!) destroy your data or config, it will just “poweroff” the running virtual machine without a clean shutdown. (don't know what happens to snapshots)