Using CoS When Many Entries Share the Same Value

CoS provides substantial benefits for relatively low cost when you need the same attribute value to appear on numerous entries in a subtree.

Imagine, for example, a directory for MyCompany, Inc. in which every user entry under ou=People has a companyName attribute. Contractors have real values for companyName attributes on their entries, but all regular employees have a single CoS-generated value, MyCompany, Inc., for companyName. The following figure demonstrates this example with pointer CoS. Notice that CoS generates companyName values for all permanent employees without overriding real, not CoS-generated, companyName values stored for contractor employees. The company name is generated only for those entries for which companyName is an allowed attribute.

Figure 12–5 Generating CompanyName With Pointer CoS

In cases where many entries share the same value, pointer CoS works particularly well. The ease of maintaining companyName for permanent employees offsets the additional processing cost of generating attribute values. Deep directory information trees (DITs) tend to bring together entries that share common characteristics. Pointer CoS can be used in deep DITs to generate common attribute values by placing CoS definitions at appropriate branches in the tree.