Dealing with an urgent mailbox size increase in Exchange 2010 DAG environment

It happens... you set a mailbox limit to an important mailbox.. and than, one day you get a call
"The mailbox is full" !!! We cannot do anything and we are losing business.

Well, the first thing to do is to assign more space to the mailbox.
If the mailbox size limit was set to inherit the Mailbox database limits defaults, you may not want to change the database defaults so not to change the mailbox size limit of all other mailboxes in the database, so go ahead and set the mailbox size limit at the mailbox level, by using the Limits tab on the mailbox properties.
Same thing goes if the limit was already set at the mailbox level - so just set a higher value to the "Prohibit send" and "Prohibit send receive" settings of the mailbox.

Now comes the tricky part...

Setting a new limit will not take effect immediately and might take up to two hours for the Information Store service to check the quota settings again and re-cache and apply the new settings.

This "Time Clock" can be tweaked to refresh more frequently by modifying the Reread Logon Quotas Interval registry key described in the following Microsoft article Mailbox Size Limits Are Not Enforced in a Reasonable Period of Time

However you need a solution and a fast one. So the quick solution will be to restart the Information Store service. However this will take cause all databases to go offline/online on a single server and will cause a fail over on a DAG scenario.

If you are using Exchange in a DAG scenario here is my suggestion:

1. Create a script to move all databases from the server to the DAG replica.
2. Move all active databases using the script to the best target available.
3. Move the database containing the mailbox you want to Super-size BACK to the original DAG member.
4. Restart the information store service on the server that contains the single mounted database.

As a result, only the mailboxes on this specific database will be effected, the restart will also cause the database to fail-over to the replicating server.
As soon as the information store is back online, move the databases back to the original server.
The Information Store is now refreshed, users experienced minimal to non of service outage, and the new size limit is applied.

I would appreciate your comments.
You can prove me wrong any day - but in a friendly manner.

Liran Zamir