HP-UX Directory Server Administrator Guide HP-UX Directory Server Version 8.1 (5900-3098, May 2013)

Because loading a long ID list from the database can significantly reduce search performance, the
configuration parameter, nsslapd-idlistscanlimit, sets a limit on the number of IDs that
are read before a key is considered to match the entire primary index.
nsslapd-idlistscanlimit is analogous to the All IDs Threshold, but it only applies to the
behavior of the server's search code, not the content of the database.
When the server uses indexes in the processing of a search operation, it is possible that one index
key matches a large number of entries. For example, consider a search for
objectclass=inetorgperson in a directory that contained one million inetorgperson
entries. When the server reads the inetorgperson index key in the objectclass index, it
finds one million matching entries. In cases like this, it is more efficient simply to conclude in the
index lookup phase of the search operation processing that all the entries in the database match
the query. This causes subsequent search processing to scan the entire database content, checking
each entry as to whether it matches the search filter. The time required to fetch the index keys is
not worthwhile; the search operation is likely to be processed more efficiently by omitting the index
lookup.
In Directory Server, when examining an index, if more than a certain number of entries are found,
the server stops reading the index and marks the search as unindexed for that particular index.
The threshold number of entries is called the idlistscanlimit and is configured with the
nsslapd-idlistscanlimit configuration attribute. The default value is 4000, which is designed
to give good performance for a common range of database sizes and access patterns. Typically,
it is not necessary to change this value. However, in rare circumstances it may be possible to
improve search performance with a different value. For example, lowering the value will improve
performance for searches that will otherwise eventually reach the default limit of 4000. This might
reduce performance for other searches that benefit from indexing. Conversely, increasing the limit
could improve performance for searches that were previously hitting the limit. With a higher limit,
these searches could benefit from indexing where previously they did not.
For more information on search limits for the server, see “Overview of the searching algorithm” (page
451).
11.5.3 Backwards compatibility and migration
While current versions of Directory Server can support the old database design, only the new
design is supported for this and later releases of Directory Server.
Upon startup, the server will read the database version from the DBVERSION file, which contains
the text Netscape-ldbm/6.2 (old database version), Netscape-ldbm/7.1 (new database
format), or bdb/4.2/libback-ldbm (new database format). If the file indicates that the old
format is used, then the old code is selected for the database. Because the DBVERSION file stores
everything per back-end, it is possible to have different database formats for different individual
back-ends, but the old database format is not recommended.
All databases must be migrated to Directory Server 8.0 when the system is upgraded. Migration
is supported for Directory Server 6.x versions, and for releases earlier than version 6.x, dump the
databases be dumped, and install Directory Server fresh. Migrating databases is covered in the
HP-UX Directory Server installation guide.
Also, the index sizes can be larger than in older releases, so you may want to increase your
database cache size. To reconfigure your cache size, look up the nsslap-dbcachesize entry
in the HP-UX Directory Server configuration, command, and file reference.
11.6 Attribute name quick reference table
Table 56 (page 468) lists all attributes which have a primary or real name as well as an alias.
When creating indexes be sure to use the primary name.
11.6 Attribute name quick reference table 467