How to add a new schema in LDAP 2.4?

Question

LDAP

Hello,
I recently encountered at work the task of adding a custom schema for LDAP. I dug up a bunch of manuals and guides on the Internet for adding my own schema, but they only refer to the old version with slapd.conf (and not OLC) and use mostly their own examples, and do not tell which ID is responsible for which type of attribute. Who can suggest a good tutorial on writing a custom schema in LDAP and using a new objectClass when creating entries.