A migration from one technology to another is a process fraught with danger. Everyone would love the "upgrade" button to work perfectly but it doesn't. Expect any migration to fail first go. Any statement that "I didn't expect to have any problems" shows inexcusable ignorance.

A release plan for a migration will typically include:

1. Business purpose for migration
2. Test migration
3. User Acceptance Testing of the test migration
4. Rollback procedure
5. Decommissioning procedure

Approved release plans are mandatory for a migrations such as:

1. Exchange Server 2003 to 2007
2. ISA Server to a hardware firewall
3. Phone system to VoIP
4. etc.​