Longer login names in AIX

User names can only be eight characters or fewer in AIX version 5.2 and earlier. Starting with AIX version 5.3, IBM increased the maximum number of characters to 255. To verify the setting in AIX 5.3 and later, you can extract the value from getconf:
# getconf LOGIN_NAME_MAX
9

Or use lsattr:
# lsattr -El sys0 -a max_logname
max_logname 9 Maximum login name length at boot time True

To