CUCM Upgrade without downtime

[a6z69@yahoo.com]

Dear All,

             We need upgrade our cucm from 12.5 Su4 to 12.5 SU8a, Kindly advise how can do this task without down time ? It's critical environment and prohibit to any interruption.

[b.winter]

If you only have 1 node, there is no possibility. Because you need to restart each node at least 1 time (for switch-over).
If you have multiple nodes, then install the new version on every node into the inactive partition and then do the switch-over node after node, so you have only one node restarting at the same time.

[a6z69@yahoo.com]

Yes we have 2 nodes:-

1- If we install new version (12.5 SU8a) at Pub & sub inactive.

2- We will register all phones at subscriber from (Cisco Unified CM Group Configuration).

3- After switch version at Publisher to (12.5 SU8a).

Can we register all phones at Publisher from (Cisco Unified CM Group Configuration) ?

What about dbreplication between Pub & Sub when Pub = (12.5 SU8a) + Sub = (12.5 SU4a), It's complete sync with status 2 ?

[Roger Kallberg]

If you make sure that you don’t restart all your CPE nodes in a CMG at the same time there should be limited affect on any services. Advice you to use the option to do a cluster upgrade instead of the older per node upgrade approach. What would be affected, and there is little/nothing to do about it, is if you have CCX as the agent login would be affected by the upgrade of CM. As long as the agent(s) stays logged in there should be no problems.

[a6z69@yahoo.com]

Somebodies complained whole cluster got database corrupted including all CUCM/IMP subscribers.
https://www.linkedin.com/posts/paul-dutcher_netarck-activity-7098449122126397440-oI9p/?trk=public_profile_like_view

[Roger Kallberg]

Every update is different and all are connected with a certain level of risk. You cannot compare your situation to another as there are simply too many variables and permutations for that.