...is "What if all the users of MySQL are suddenly invaded by an Oracle salesperson who says pay up?" Let's say Oraclecreates certain anticompetitive practices in which they try to corral all of these millions of users on the MySQL database...
http://news.cnet.com/8301-1001_3-10346175-92.html
...one of the most important factors in the write performance for Oracle databases. Whenever a database write occurs, Oraclecreates a redo entry. Redo logs are used in sequence with the best practice configuration using mirrored redo log groups...
http://www.texmemsys.com/files/f000139.pdf