Is it OK to uninstall the Master-Agent when Leafs exist?

In general, NO!

When you uninstall the Master-Agent, all the Leaf-Agent "registration" data is lost, including ID information and encryption key data supporting secure communications between Master and Leaf(s).

This "orphans" the Leaf-Agent machines and requires that you uninstall and reinstall all the Leafs again for the new Master-Agent. For a few Leafs, this is an inconvenience. For a couple hundred Leafs, this becomes a very time-consuming issue!

Since there is not an easy way to manually rebuild this data, the AgentUtil.exe utility was added with the UpdateEXPERT6.1 release (Not 6.0) to allow backup and restore of Leaf-Agent data.

Please, if you want to un-install a Master-Agent, and you have Leaf-Agent connections, use the AgentUtil.exe link above to get familiar with the migration tool. If you feel you need help, contact support for assistance or to verify that what you want to do makes sense.