Steps How to install CU for Skype for business 2015 when you have only on Front end server in the Enterprise edition pool.

Technically It's pretty much straight forward, but of course having one Front End Server has always a risk.

We have also same situation with Lync 2013, but I installed the equilvant Patch on the 2013 version and it worked fine.

1. Get the latest CU from here https://technet.microsoft.com/en-us/office/dn788954.aspx
2. Look at the instructions provided here:
https://support.microsoft.com/en-us/help/3061064/updates-for-skype-for-business-server-2015
In your case you will need to start form step three Run the Cumulative Server Update Installer, and then click Install Updates to upgrade the server role. Step 1 and 2 is only when you can Failover SfB

3.  When You downlod the CU updateds it will show you what will be Updates. I'm pretty sute that one of the updates will contain Core. Because of that Yo need to do it out of hours as doing the installtion the Lync Services will be stopped, and started after installation
4. After the Update reboot the Lync Server
5. Make sure Services Came up, and check the Event Viewer for any errors.
6. Repeate same for Edge Servers or any other servers you have in Topology describe in this article:
https://support.microsoft.com/en-us/help/3061064/updates-for-skype-for-business-server-2015

So you do this:

Run the Cumulative Server Update Installer, and then click Install Updates to upgrade the server role.
"Run as Admin" If you have UAC enabled.

Then you need to run the SQL Update Cmdley
If this is an Enterprise Edition Back End Server and there are no collocated databases on this server, such as Archiving or Monitoring databases, type the following at a command line:

Install-CsDatabase -Update -ConfiguredDatabases -SqlServerFqdn <SQL Server FQDN>

If this is an Enterprise Edition Back End Server, and there are collocated databases on this server, type the following at a command line:

Install-CsDatabase -Update -ConfiguredDatabases -SqlServerFqdn <SQL Server FQDN>  -ExcludeCollocatedStores


The CSDatabase in our Environment is the only part where i have problem becasue:
1. You need to run that command with a account where you have access to the database
2/ You need to know if  the SQL Server you are using is standalone or collocated with other databases.

Make sure with your DBAs that the account you will be logged in to SFB and run the comand has all permissions.

If you have that you should be ok and ready to go.

Thanks a lot for your inputs this makes me more comfortable now.
Just to add few things before i can go ahead with the above steps and need your input is.

I have 2 FE pools in first pool i have 3 FE SFB 2015server and second pool i have only 1 FE SFB 2015 server.
the first pool is backup pool for second FE pool and vice versa for second pool as well.

So in this case do i need to do anything extra or just first simply go ahead and install the 2nd enterprise Pool (with single FE) with above steps and follow the same article from step one for the 1st pool

Thanks this info helped a lot cheers!!!