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ERROR_DS_ATT_NOT_DEF_IN_SCHEMA
The directory cannot resolve the attribute definition
ERROR_DS_ATT_NOT_DEF_IN_SCHEMA means that Active Directory encountered an attribute reference for which no usable schema definition is available. This is earlier than an object-class permission check: the server first needs an attributeSchema object that identifies the attribute and its syntax.
Typical causes are a misspelled LDAP display name, an LDIF import applied in the wrong order, a schema extension that has not replicated to the handling domain controller, or an application using a vendor-specific attribute before the extension has been installed.
Checks that give evidence
- Query the schema naming context from
rootDSE, then look up the intendedattributeSchemabylDAPDisplayName. - Compare the LDAP display name used by the client with the schema object. Do not substitute the schema object's
cnor a user-interface display name without confirming the mapping. - Confirm that the schema change was made on the schema master and has replicated to the domain controller receiving the application request.
- Review the LDIF dependency order: class definitions may refer only to attributes that have already been defined and activated.
Why a retry alone is weak evidence
A retry can succeed only if a replication or deployment race has completed. When the name itself is wrong or the extension was never installed, retrying merely repeats the same schema lookup failure.
References
- Microsoft: schema container and forest-wide replication
- Microsoft: attributeSchema characteristics
- RFC 4512: LDAP attribute types and schema
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