http://blogs.technet.com/b/momteam/archive/2014/09/19/iis-log-format-requirements-in-system-center-advisor.aspx
However, once machines are added into OMS, it's entirely possible the IIS logs are changed, new sites are rolled, etc. And there is no easy way to see if that had been done, or stay on top of it.
As a solution I throw an alert in SCOM if any site is not configured to 'hourly'.
As a solution I throw an alert in SCOM if any site is not configured to 'hourly'.
See my TechNet wiki articlefor a howto, and a handy script to set up IIS Log rollover via PowerShell.