I disagree with the previous poster's sentiments that one shouldn't take the exam unless one has a job lined up first.
Taking the exam is not very onerous. It's something one can easily study for in one's spare time. And once you have the licence you can go for any FISO job that comes up, and you will be available to start immediately. This puts you in a much better position than someone who replies to a job advert saying "I am very interested, will you consider me once I have taken the exam in three months' time?" (Exams are only held four times a year, on the last Thursday of January, April, July and October)