Arcane spell failure and long casting times

[Neils Bohr]

If I cast a spell with a casting time longer than one standard action, and had somatic components, in armor when does the spell fail?
For example, if I cast a spell that takes a full round and fail due to arcane spell failure, can I take my move action, or am I locked into a failed spell for a full round?

[David knott 242]

I wouldn't make the check until you finish casting the spell, specifically to avoid the question you asked. The rules say that the check is made when you cast the spell, not when you begin casting it -- so you should have used up the casting action(s) before you even attempt the check.

[James Risner]

You don't know if you botched the somatic until the spell takes effect, once you've completed casting.

[Neils Bohr]

That makes sense, thanks a lot. I was getting tripped up on the vagueness of it