logfile format?

Does anyone have the format that the logfile for informix SE engine is in? Also, is it something the changes from version to version? Regarding Online: What kind of problems are people running into with regards to relying completely on informix tools? I may be under the group of people that are "scared of what they can't see". I like the idea of backing up with tar and knowing I can trot over to another machine and read the table onto it. Does everyone running Online currently have a dedicated tape drive for its use? Thanks, Paul