If you've been running SAM with additional pollers, you're no doubt aware that you had a choice between the Poller-Bound option, or the Local-Only option.
Normally, an administrator would use the Local-Only mode to control which ports are open between SAM and the managed nodes (a security feature of sorts). Selecting this option also allowed you to more evenly balance the load of the additional pollers. The Poller-Bound option meant SAM would need to be installed on every polling engine.
Nothing if you don't use additional pollers, or have been using the Poller-Bound option all along. However, if you are in the minority and want to preserve the effect of local polling provided by earlier versions of SAM, you will need to migrate all nodes with applications assigned to them to the primary SAM server. (We made it easy for you.) Simply follow the instructions in this article and run the attached report. (I know, sometimes change sucks, but we're here to help.)