Not all schema changes are allowed. See Disallowed schema changes for change restrictions.
Web administration
If you have not done so already, expand Schema management in the navigation area, then click Manage object classes. To delete an object class:
Command line
View the object classes contained in the schema issue the command:
ldapsearch -b cn=schema -s base objectclass=* objectclasses
Select the object class you want to delete and issue the following command:
ldapmodify -D <adminDN> -w <adminPW> -i <filename>
where <filename>contains:
dn: cn=schema
changetype: modify
delete: objectclasses
objectclasses: (<myobjectClass-oid>)