I import reference to LDAP users and groups to my database.
Therefore, I need to synch these users and groups periodically.

It is clear for me how to synch these object when LDAP supports Unique Identifier (UID).
For example Active Directory support `objectGUID` attribute.

In this case when a user (or group) is moved to other place in LDAP tree and therefore its DN is changed I still can find it using UID and update the user.

What to do when LDAP does not support UID and DN is changed?

If I looking using old DN I can not find a user (or group) and need to remove the user.

But how can I distinguish between use cases when a user is moved to other place in the LDAP tree (its DN is changed) and a user is deleted from LDAP?

When it moved I should find it and update to new DN.
When it is deleted I need to remove it.

I do not know how to do it.

Can I use the username (login name) for the user synchronization?

What I should use for LDAP group?