determining what schema are loaded

I've been tasked with adding a mail attribute for an openldap 2.4.23 installation. I've read enough of the entries on the mailing list that talk about the inability to do so being related to the proper schema not being loaded, and I think that is the issue.

What I'm struggling with, is how to determine what schema are loaded and where they are loaded from? In reading the Redhat documentation, they reference

Required attributes are specified using the objectClass definition, and can be found in schema files located in the /etc/openldap/slapd.d/cn=config/cn=schema/directory.

So does this mean that in the above referenced directory, those schema will be loaded?