About Attribute Uniqueness

The attribute uniqueness feature prevents duplication of attribute values, both when adding and modifying them. For example, it prevents you from assigning to a new employee an identifier already assigned to another employee. Instead, the directory server terminates the operation and returns an error message.

You can define attribute uniqueness:

• Across the entire directory

  For example, to ensure that every entry in your directory that includes a mail attribute has a unique value for that attribute, you create an instance of attribute uniqueness associated with mail.

• Across one subtree for each attribute

  For example, suppose that MyCompany hosts the directories for SubscriberCompany1 and SubscriberCompany2. You can enforce attribute uniqueness in SubscriberCompany1 only.

• Across one object class

  For example, ID is an attribute in both the machine object class, and the person object class. If attribute uniqueness is enabled, then the directory server prevents you from adding either two machines or two people with the same ID. However, a machine ID attribute can have the same value as a person ID attribute.

To implement attribute uniqueness, you create an attribute uniqueness constraint entry in which the attributes in Table 8-1 are specified.

Table 8-1  Attribute Uniqueness Constraint Entry

Attribute Name	Mandatory?	Valid Value	Default Value	Default Effect
orcluniqueattrname	Yes	Any string	N/A	N/A
orcluniquescope	No	One of the following: base--Searches the root entry only onelevel--Searches one level only sub--Searches the entire directory	sub	Searches the entire directory
orcluniqueenable	No	Either 0 (disable) or 1 (enable)	0	Disables attribute uniqueness
orcluniquesubtree	No	Any string	" "	Searches the entire directory
orcluniqueobjectclass	No	Any string	" "	Searches all object classes

When you have created the entry and specified the attributes, before it performs an operation, the directory server:

• Uses the attribute uniqueness constraint to check all update operations

• Determines whether the operation applies to a monitored attribute, subtree, or object class

If an operation applies to a monitored attribute, suffix, or object class, and would cause two entries to have the same attribute value, then the directory server terminates the operation and returns a constraint violation error message to the client.

Note: The attribute uniqueness feature works on indexed attributes only.