There is the limit and the possibilities of your machines.
setopt BANG_HIST # Treat the '!' character specially during expansion.
setopt EXTENDED_HISTORY # Write the history file in the ":start:elapsed;command" format.
setopt INC_APPEND_HISTORY # Write to the history file immediately, not when the shell exits.
setopt SHARE_HISTORY # Share history between all sessions.
setopt HIST_EXPIRE_DUPS_FIRST # Expire duplicate entries first when trimming history.
setopt HIST_IGNORE_DUPS # Don't record an entry that was just recorded again.
setopt HIST_IGNORE_ALL_DUPS # Delete old recorded entry if new entry is a duplicate.
setopt HIST_FIND_NO_DUPS # Do not display a line previously found.
setopt HIST_IGNORE_SPACE # Don't record an entry starting with a space.
setopt HIST_SAVE_NO_DUPS # Don't write duplicate entries in the history file.
setopt HIST_REDUCE_BLANKS # Remove superfluous blanks before recording entry.
setopt HIST_VERIFY # Don't execute immediately upon history expansion.
setopt HIST_BEEP # Beep when accessing nonexistent history.
From the ZSH Mailing list:
You should determine how much memory you have, how much of it you
can allow to be occupied by the history (AFAIK it is always fully
loaded into memory) and act accordingly. Removing the limit is not
wiser as it leaves you with an idea that there is no limit while it
is always limited by available resources.
Or if you do not think you will ever hit a problem with resource
exhaustion you can just set HISTSIZE to LONG_MAX from limits.h: it
is the maximum number HISTSIZE can have.
Which explain the Gentoo solution:
History won't be saved without the following command:
To prevent history from recording duplicated entries (such as ls -l entered many times during single shell session), you can set the hist_ignore_all_dups option:
A useful trick to prevent particular entries from being recorded into a history by preceding them with at least one space.