Service manual

Costs: How Updates Affect Indexes
128 Sun ONE Directory Server Installation and Tuning Guide • June 2003
In general, tuning indexing for an instance of Directory Server means maintaining
onlythose indexes for which the benefits from faster search processing offset the
costs of more update processing and of more space needed. Maintaining useful
indexes is good practice; maintaining unused indexes for attributes on which
clients rarely search is a waste.
Presence Indexes
Figure 7-1 depicts a presence index for the nsRoleDN attribute, showing how this
index is independent of the attribute value, but simply includes all entries in the
database having an
nsRoleDN attribute.Every value of the attribute matches *.
Figure 7-1 Representation of a Presence Index
As shown, the internal entryid attribute value allows Directory Server to store a
reference to the entry that allows for quick retrieval. Directory Server actually
retrieves the entry using the dbinstance
_id2entry.db3 index file, where dbinstance
depends on the database identifier as implied in “About Indexes,” on page 125.
When Directory Server receives an update request for an entry having an attribute
indexed for presence, it must determine whether the entry must be removed from
the index or not, and must then carry out any necessary modifications before
returning acknowledgement of the update to the client application.
Thecost of presenceindexesis generally lower thanfor other index types, although
the list of entries maintained for a presence index may be long.
*
Entry IDs
# entry-id: 23
dn: uid=yyorgens,ou=People,dc=example,dc=com
objectclass: top
objectclass: person
objectclass: organizationalPerson
objectclass: inetOrgPerson
uid: yyorgens
givenName: Yolanda
sn: Yorgenson
cn: Yolanda Yorgenson
mail: [e-mail]
secretary: uid=bcubbins,ou=People,dc=example,dc=com
nsRoleDN: cn: managers,ou=People,dc=example,dc=com
nsroledn
entryidentryid entryid entryid entryid entryid entryid entryid entryid ...