With OrientDB 1.6:
(1) Open the console with 1.6:
cd $ORIENTDB_HOME/bin ./console.sh
(2) Connect to database and export it:
orientdb> connect plocal:/mydirectory/mydb admin admin
orientdb> export database /temp/mydb
orientdb> exit
(3) Now open the console with 1.7 and:
orientdb> create database plocal:/mydirectory/mydb2 admin admin plocal
orientdb> import database /temp/mydb
By the way once 1.7-rc2 will be ready it will allow to "old" database to get used without export/import.