File Extension SOS File Format EnSight Master server file SOS stands for EnSight Master server file. This was last updated in March 2012 By Margaret Rouse Browse File Extensions Alphabetically: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Ask a Question. Find an Answer. Ask your peers a question about this file extension. Ask a Question Problem with SQL Server Database File(.mdf) Recovering deleted records SAP Business One - Attaching a file without the file being copied to the "Attachment" file.