CUCM Upgrade Non Service affecting documentation

[joeharb]

I have performed multiple CUCM upgrades on different clusters in the past, but now I am getting questioned on our latest corporate update.  I performed the upgrade over a weekend in February without issues, but our audit department has now come back and stated that since this could be service affecting there should have been other procedures in place.  We have 1 pub and 5 subs.  The upgrade was not a refresh upgrade (and even if it was I only do one server at a time) and there was no instance that phones or incoming calls were not functional.  I need any type of documentation that states that an upgrade (if performed "correctly") is not service affecting.

Thanks,

Joe 

[Jaime Valencia]

I don't think you will find any document that states that, because there are many things to consider, and even if you're doing a "correct" upgrade that doesn't translate into no service disruption.

In a single server cluster, you can perform a perfect upgrade, and you'd still have service disruption because there is no failover.

If you choose to reboot a pair of subscribers which are in the same UCM group, that is a perfectly valid option in an upgrade to minimize time, and you'd have service disruption for the phones that use those subscribers.

Your audit department needs to understand that whether an upgrade causes service disruption (or not) will depend on whoever planned and executed the upgrade based on the specific deployment.

[TONY SMITH]

It's definitely service affecting as the phones will re-register from one server to another.  And unfortunately it's not easy to predict what exact time these brief interruptions are going to happen.  The best that I've managed was to upgrade Publisher and Backup Subscribers in one session, which is not service affecting.  Then manually and at an agreed time force phones to switch to the backup before progressing with upgrade of the live Subscribers.