Server 11 and Server 12 cannot be run on the same machine.
FileMaker 12 (.fmp12) files can only be opened in v12
FileMaker 11 (.fp7) files can only be opened in v11
"I assume there is not problem running Server 11 and Server 12 on the same server."
Don't even attempt to install both on one machine. It cannot be made to work for a variety of reasons which are well documented. In fact, you MUST UNinstall one before installing the other or things will go wrong.
Sorry about that...