Database & Connection String Changes
The easiest way to change the connection string is to have the old and new databases working at the same time. If this is the case you can simply change the connection string in the corresponding sites Admin > Settings module before removing the old database.
If the old database is corrupt or you have already deleted it, you will have to manually update the connection strings in the corresponding sites web.config file. After this has been done the master or web site console should load, but you still have to update Centralpoint. To do this you simply go to the Admin > Settings module and submit the page without making any changes.