HP-UX Directory Server 8.1 administrator guide

11.1.2.2 Overview of system indexes
System indexes cannot be deleted or modified. They are required by the directory to function
properly. Table 11-2 “System indexes” lists the system indexes included with the directory.
Table 11-2 System indexes
PurposePresEqAttribute
Allows the Directory Server to quickly obtain the access control information
maintained in the database.
aci
Used to help accelerate subtree searches in the directory.objectClass
Speeds up entry retrieval based on DN searches.entryDN
Enhances directory performance during one-level searches.parentID
Used by the Directory Server Console to enhance display performance on the
Directory tab.
numSubordinates
Used to search for specific entries.nsUniqueID
11.1.2.3 Overview of standard indexes
Because of the need to maintain default indexes and other internal indexing mechanisms, the
Directory Server also maintains certain standard index files. The standard index, id2entry.db4,
exists by default in Directory Server; you do not need to generate it.
The id2entry.db4 contains the actual directory database entries. All other database files can
be recreated from this one.
11.1.3 Overview of the searching algorithm
Indexes are used to speed up searches. To understand how the directory uses indexes, it helps
to understand the searching algorithm. Each index contains a list of attributes (such as the cn,
common name, attribute) and a pointer to the entries corresponding to each value. Directory
Server processes a search request as follows:
1. An LDAP client application such as the ldapmodify command, sends a search request to
the directory.
2. The directory examines the incoming request to make sure that the specified base DN matches
a suffix contained by one or more of its databases or database links.
• If they do match, the directory processes the request.
• If they do not match, the directory returns an error to the client indicating that the suffix
does not match. If a referral has been specified in the nsslapd-referral attribute
under cn=config, the directory also returns the LDAP URL where the client can
attempt to pursue the request.
• If the search request for each database attribute can be satisfied by a single index, then
the server reads that index to generate a list of potential matches.
• If there is no index for the attribute, the directory generates a candidate list that includes
all entries in the database, which makes the search considerably slower.
• If a search request contains multiple attributes, the directory consults multiple indexes,
then combines the resulting lists of candidate entries.
• If there is an index for the attribute, the directory takes the candidate matches from the
index files in the form of a series of entry ID numbers.
3. The directory uses the returned entry ID numbers to read the corresponding entries from
the id2entry.db4 file. The Directory Server then examines each of the candidate entries
11.1 About indexes 453