Managing Indexes368 Netscape Directory Server Administrator’s Guide • May 2002When 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 everysingle entry 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.When All IDs Threshold is Too HighSetting the All IDs Threshold too high can also cause performance problems. Anexcessively high All IDs Threshold results in large entry ID lists that must bemaintained and loaded into memory when servicing search requests. Anexcessively high All IDs Threshold can eliminate all of the benefits of the All IDsmechanism (see “Benefits of the All IDs Mechanism,” on page 367 for details).All IDs Threshold Tuning Advice for Single-Enterprise DirectoriesBe careful when changing the default All IDs Threshold value for your server. Ifyou change the threshold to an inappropriate value, you can compromise ratherthan improve your server performance. This tuning advice is intended primarilyfor single-enterprise directories of up to 80,000 entries.
