OCaml and Haskell share a common ancestry, but I would also draw a distinction between them. (Though not the same that the other commenter did.)
OCaml is a bit more of a drop-in replacement for something like C++ or D. Mostly because it's strict by default, so it's easier to reason about performance even for a non-expert user.
OCaml's approach to side-effects has now entered the mainstream: it's considered good style to avoid them, but they are still used pervasively. That's very similar to what good modern C++, Java, Python etc style advocates.
Of course, Haskell also allows side-effects. But generally, you track that they are occurring with the type system, you generally stick them in some kind of Monad or Applicative Functor.
OCaml is a bit more of a drop-in replacement for something like C++ or D. Mostly because it's strict by default, so it's easier to reason about performance even for a non-expert user.
OCaml's approach to side-effects has now entered the mainstream: it's considered good style to avoid them, but they are still used pervasively. That's very similar to what good modern C++, Java, Python etc style advocates.
Of course, Haskell also allows side-effects. But generally, you track that they are occurring with the type system, you generally stick them in some kind of Monad or Applicative Functor.