Sometimes when password rules are very strict, a user may have problems creating a new password that is both easy to remember, and still adheres to the password rules. To aid the user, it could be useful to clear the password history for his or her account. The password history is stored in /etc/secuirty/pwdhist.pag. The command you use to remove the password history is:
# chuser histsize=0 username
Actually, this command not only removes the password history, but also changes the setting of histsize for the account to zero, meaning, that a user is never checked again on re-using old passwords. After running the command above, you may want to set it back again to the default value:
# grep -p ^default /etc/security/user | grep histsize
histsize = 20
