I am looking to buy anti theft accessory for my bike & after exploring various options i am considering good quality chain lock and need your opinion. I will require to lock my bike only when i park my bike in beach or open ground and not in my home or office as there is adequate security here. So how effective is heavy duty chain lock in preventing theft of bike especially in public place?

Below are the other anti-theft accessories i came across & i am not considering them for below mentioned reasons:
I don't want to buy anti theft alarm as there is chance of it giving false alarm especially when i am not in earshot & this will become nuisance for others in vicinity.
GPS tracking system is beyond my budget.
I heard Disc brake lock can easily removed using a tool within a minute, so iam not considering it either.