I have 4 active directory servers as below.
dc1 windows 2003, runs dns, dhcp, global catalog
dc2 windows 2008 standard, runs dns, global catalog ( handling FSMO roles)
dc3 windows 2008 standard , dns
dc 4 windows 2012 standard
I need to migrate my domain level and make the windows 2012 the primary ( fsmo ) and remove the windows 2003, what is the best and recommend way to have a stable active directory in my network