Anyways, I wanted to talk about a problem you might face (certainly I have faced recently) in a situation when your DAG members are online but the database fails to activate to a particular node! Back in the days that used to happen if one of your Exchange vital services has stopped, but in this scenario all services were running as normal.
Based on Activation preference on each DB, I wanted to redistribute DB’s between all nodes after a restart. MS has kindly written a beautiful script that could take care of that for you based on a specific DAG. RedistributeActiveDatabases.ps1 which is located under Exchange install directory inside a ‘Script’ folder. This script can take your DAG and assess DB distributions, based on their activation preferences it starts to move the active DB’s to their intended servers.
In my case it failed to move due to some error on the server regarding ‘HighAvailability’ state, Exchange 2013 has introduced a new concept of server component state, which gives a granular control over server components that make up the Exchange server.
Running Get-ServerComponentState -Id ServerName on an Exchange server would show each of the component running and their state, this is very useful in troubleshooting problems with Exchange before even digging deep into configuration.
In order to bring server components online you could run the following PowerShell command:
Set-ServerComponentState -id ServerName -Component ComponentName -State StateName -Requester FunctionName
Note, if components were brought online by multiple requesters then you would need to issue the ‘Active’ command state under both these requesters in order for the component to turn to active.
There is a great article written by the Exchange team which goes in great depth explaining the principle behind it and the advantages gained by the administrator.