The history is shared between my iTerm2 terminal tabs: how can I switch that off?

I am using iTerm2 (with zsh), and for some reason the history is shared between the different tabs and windows that are open. In most of the cases for me, this is annoying, since I have tabs per specific task, and if I have to redo some commands, I just want to be able to go back (up) in history to retrieve the last action for that window/tab only.

I have no idea how to disable this shared history, I read somewhere that you can enable shared history in zsh, but afaik I have done no such thing.

Can anybody point me in the right direction?

Executing the following should do the trick (use setopt to reenable them):

unsetopt inc_append_history
unsetopt share_history