vzmigrate --online dest-host VEIDNO
vzmigrate --oneline 192.168.1.55 101
One option I would recommend is "--keep-dst", that way if the migration is interrupted you can still bring the VPS back up on the original host. After the migration is successful you can manually destroy it.
OpenVZ has a good writeup on this including Checkpointing and Restoring etc: http://wiki.openvz.org/Checkpointing_and_live_migration
openvz, vzctl, migration, downtimevzmigrate, online, dest, veidno, eg, vzmigrate, oneline, quot, dst, interrupted, vps, manually, writeup, checkpointing, restoring, etc, http, wiki, org, checkpointing_and_live_migration,