Other notable areas inside of the Mega include the O'Mega Mess (the Junior Ranks Mess and popular after hours area for recruits), the Patriot Club (Senior NCO and Officer's Mess).
The text describes two distinct areas within a larger structure called "the Mega." The first is the O'Mega Mess, which serves as both a Junior Ranks Mess and a social space for recruits.  The second is the Patriot Club, designated as a gathering place for Senior NCOs and Officers.