The default value for MAXDAYS and MINDAYS is zero if not specified.
To create a logonid with a non-expiring password the MAXDAYS field should be set to zero (zero is the default) and LIDZMAX bit field should be set in the logonid. Setting the LIDZMAX bit field in the logonid record will insure the MAXDAYS zero settiing will be enforced regardless of the global GSO PSWD PSWDMAX field setting.
The ACF2 logonid field MAXDAYS and MINDAYS default values are zero if not specified.
The MAXDAYS field specifies the maximum number of days (based on the date specified in the PSWD-TOD field) permitted between password changes before the password expires. The MINDAYS specifies the minimum number of days that must elapse before a user can change their password.
LIDZMAX and LIDZMIN are only required to override non-zero GSO PSWD PSWDMAX and PSWDMIN values when the logonid fields MAXDAYS or MINDAYS are set to zero.
Details regarding MAXDAYS, MINDAYS, LIDZMAX and LIDZMIN can be found in the CA ACF2 for z/OS Administrator Guide in Chapter 3: Maintaining Logonid Records, section "Logonid Record Fields".
Details regarding the GSO PSWD PSWDMIN and PSWDMAX fields can be found in the CA ACF2 for z/OS Administrator Guide in Chapter 14: Maintaining Global System Options Records, section "Password Maintenance and Support (PSWD)".