Object class violation -- attribute nisMapName

[Thomas J Pinkl <tom@hbsrx.com>]

I'm having a problem with OpenLDAP 1.2.11 running on a 
SCO OpenServer 5.0.5 platform.  When I attempt to use 
MigrationTools 3.24, it produces this fragment of LDIF:

  dn: nisMapName=netgroup.byuser,dc=hbsrx,dc=com
  nisMapName: netgroup.byuser
  objectClass: top
  objectClass: nisMap
  objectClass: domainRelatedObject
  associatedDomain: hbsrx.com

When this entry gets processed by ldapadd, I get:

  adding new entry nisMapName=netgroup.byuser,dc=hbsrx,dc=com
  ldap_add: Object class violation

And in the syslog, I find:

  Aug  7 16:49:33 myldap slapd[12346]: Entry (nisMapName=netgroup.byuser,dc=hbsrx,dc=com), attr "nismapname" not allowed 
  Aug  7 16:49:33 myldap slapd[12346]: conn=1 op=1 RESULT err=65 tag=105 nentries=0 

My slapd.conf file has "schemacheck on" and includes the standard 
OpenLDAP attribute and objectclass .conf files.  It also includes 
my own attribute and objectclass files, where I have these lines:

(in hbs-slapd.at.conf)
attribute nisMapName                   1.3.6.1.1.1.1.26  ces
attribute nisMapEntry                  1.3.6.1.1.1.1.27  ces

(in hbs-slapd.oc.conf)
objectclass nisMap
        requires
                objectClass,
                nisMapName
        allows
                description

These, of course, come from RFC2307.

By setting the appropriate loglevel and re-starting slapd, I've 
confirmed that it "sees" these entries.  So why am I getting 
"Object class violation"?

-- 
Thomas J. Pinkl                         738 Louis Drive
Unix Systems Programmer                 Warminster, Pa 18974
Health Business Systems, Inc.           (215) 442-9300 x9260