As customers plan to upgrade their Cisco Unified Communications Manager to take advantage of new features, and if the upgrade includes moving to virtual machines, the procedural steps to accomplish these tasks are not clear. Cisco does provides documentation on how to upgrade, how to migrate to a virtual machine and what versions/servers are supported, but there is no one document that combines these 3 key areas into a single document that details the 'best practices' for planning an upgrade and migration.
The Operational Guide for Cisco Communcations Manager is the one document that details the best practices for upgrading and migrating to Cisco Unified Communications Manager v9.x. The document details upgrade from 6.x/7.x/8.x installs on physical MCS servers to 9.x servers running in a virtual machine.