Should an Informix account, local vs. LDAP.
For the actual Informix account, The preference for local authentication rather than LDAP. Using local
removes an entire layer of configuration and set up just to be able to administer an instance. This is particularly important during any
downtime where some or all elements of remote authentication is down or disabled and prevent end-users from accessing services.
The Informix user ID should always be able to connect to the instance at all times. The most reliable way to do this is through local authentication.
Please see link below on how to configure LDAP