Use a load file if your LDAP JNDI Adapter(s) are configured for read-write.
The process will fail if the user account already exists.
We need more information to provide a decent response.
What LDAP are you using with Windchill and how is your Windchill configured for defining users?
If your LDAP JNDI Adapter(s) are configured read-only (e.g. Active Directory or other corporate LDAP), then users are created by the IT department. They would use an LDIF file to load user accounts. They will be visible to Windchill once the accounts exist in LDAP and are visible to Windchill (i.e. under the search base and member of the LDAP "filter" group,
If your LDAP JNDI Adapter(s) are configured read/write (e.g. openDJ or other Windchill dedicated LDAP), then you can use loadFromFile to create users.
Using OpenDJ, there are too many users, and creating them one by one is too slow.
Use a load file if your LDAP JNDI Adapter(s) are configured for read-write.
The process will fail if the user account already exists.