Well the New Year is now in-play and completing a major Year-2 True-Up for a large Microsoft Enterprise Agreement provided a prompt to refresh on the Windows Server 2016 conversion prior to those nasty renewals that come around so soon.
Much like the SQL Server 2014 migration the Windows Server 2016 shift (which started from October 2016) presents an opportunity for customers with active SA to transition their processor based licenses to core based ensuring coverage is gained across the full physical cores in their environment.
Essentially, where you have a ‘server density’ of 8 cores or less per processor and 16 cores or less per server a full license grant is assumed – there is no need to record your environment as you’ll get the full complement of licenses by default.
If however your server density is higher there’s some work to be done! You’ll need to ensure your entire Windows Server landscape is inventoried and formally documented ready for the expiration of your current SA, at which point you’ll only pay the additional SA, not additional licenses. But if you are not prepared and time gets away on you there’s potentially significant cost down the track as those uncounted cores come to light (the dreaded audit perhaps), so it pays to get organised and active way before your renewal date.
And as a postscript - if you're using subscription licenses be aware that although you can vary down at anniversary, if you varied up at any time during the year - well that applies from the date of install.