Managing Indexes366 Netscape Directory Server Administrator’s Guide • January 2002• Does not have to load unnecessarily large entry ID lists into memory inresponse to search requests that result in all directory entries anyway, thusincreasing search performance by reducing large disk reads• Does not require large amounts of RAM to hold in memory unnecessarily largeentry ID listsDrawbacks of the All IDs MechanismPerformance problems can occur if the All IDs threshold is set either too low (this isthe most common problem) or too high for your directory’s size.When All IDs Threshold is Too LowWhen you set the All IDs Threshold too low, too many index keys will contain theAll IDs token. This can result in too many directory searches examining every entryin your directory. The performance hit on searches can be considerable.For example, suppose you are managing an equality index on the common name(cn) attribute. One of the index keys stored in your cn index is cn=James. Thecorresponding entry ID list contains the ID number of every entry containing anattribute that is set to James.The equality index on the cn attribute is easy to maintain because only smallfraction of the entries in your directory will include cn=James. Performance forsearches that use a cn=James filter will be improved because only that smallfraction of entry IDs needs to be examined when servicing the search request.However, over time your directory may continue to grow. As it does, more andmore James may be added, but at the same relatively small proportion of totaldirectory entries. Eventually, the cn=James entry ID list can become quite large,but it will still be a list that is necessary for search performance. If your directorygrows large enough that so many cn=James entries are added that the All IDsthreshold is met, then the cn=James entry ID list is replaced with an All IDs token.Every time you search for cn=James, the directory server will examine every singleentry in the directory in response to the search request.When the database grows large, the All IDs threshold will be set for a largepercentage of all index keys and your search performance will significantlydegrade.
