The Simulation Mode is activable next to the “Start Job” button.
It will make the Job to run in a “read-only” mode : the read operations will be performed, but any “write” operation will be logged in a LOG file :
In a basic File to Database Job, the result would be like this :
As you can see, the “INSERT” statements are only logged in the file, which can be helpful if you simply need some SQL code without using Fuzible 😉
But, in general, the Simulation Mode is a good tool if you want to carefully try your Job, or just give you an idea on how it will behave.