Password History is a list of passwords maintained by OpenVMS for each user record. All new passwords set by the user with SET PASSWORD are checked against the user's password history unless the DISPWDHIS flag is set in the user record.
The period of time during which passwords are stored in the password history list is defined by the SYS$PASSWORD_HISTORY_LIFETIME logical and by default is 365 days (the maximum is 28000 days). It should not be set to less than PWDLIFETIME in the user record. The default size of the password history list is 60 words; it can be controlled with the SYS$PASSWORD_HISTORY_LIMIT logical (the maximum is 2000 words). Note that these values should be consistent across all nodes in the cluster.
The password history list is located in SYS$SYSTEM:VMS$PASSWORD_HISTORY.DATA. You can move the list off the system disk by using the logical name VMS$PASSWORD_HISTORY. It should be defined in the system table in executive mode in SYLOGICALS.COM.