I would say that only the IBM Redbooks. Please check them at IBM's 340 certification site and this forum as well.
At 340 exam Yahoo group, you will find some useful information like: - Chapters which you should study in order to prepare. It is a very good hint because the study material is huge (more than 3K pages) - Mock exams from IBM pre-assestment test
The Barcia's book is very good written. Unfortunately it is focused mainly on WAS scripting language.
I failed a couple of months ago (01 question :-( ). It is not difficult but experience talks. They ask a lot of dumb questions, like: - log/configuration files - You must know their names, location and functionality. - Settings - You should know what they mean and default values as well (yes, they asked this) - TCP Ports - You should memorize all them. They asked me for some that I think that they are not relevant. - script language - Unbelievable, but they ask for the same command, different set of parameters. At my exam, they asked for a command which was not available at IBMs Admnistration Redbook.
Good luck. It is not the smartest exam (I'd rather prefer 287 or 484) so be prepared those kind of tricky questions.