We are currently using unity 3.1
We are going to have fresh installation on the new machine with unity 4.0(5). How is the migration work for export/import database on different version and also different machine.
You cannot use DiRT to backup from one version of Unity and import into another. You will either need to upgrade the existing server to 4.0(5), backup the data and restore to the new 4.0(5) server or backup the existing 3.1 data, install 3.1 on the new server, restore the 3.1 data, and upgrade the new server to 4.0(5). Take a look at the links below.
Upgrading Cisco Unity 3.x Software to the Shipping Version
Replacing or Converting a Cisco Unity Server or Failover Servers
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