Drawbacks Of The All Ids Mechanism; When All Ids Threshold Is Too Low - Netscape DIRECTORY SERVER 6.2 - ADMINISTRATOR Administrator's Manual

• Does not have to maintain infinitely increasing entry ID lists, thus minimizing
your Directory Server's disk space usage
• Does not have to load unnecessarily large entry ID lists into memory in
response to search requests that result in all directory entries anyway, thus
increasing search performance by reducing large disk reads
• Does not require large amounts of RAM to hold in memory unnecessarily large
entry ID lists

Drawbacks of the All IDs Mechanism

Performance problems can occur if the All IDs threshold is set either too low (this is
the most common problem) or too high for your directory's size.

When All IDs Threshold is Too Low

When you set the All IDs Threshold too low, too many index keys will contain the
All IDs token. This can result in too many directory searches examining every entry
in your directory. The performance hit on searches can be considerable.
For example, suppose you are managing an equality index on the common name
( ) attribute. One of the index keys stored in your
cn
corresponding entry ID list contains the ID number of every entry containing an
attribute that is set to
The equality index on the
fraction of the entries in your directory will include
searches that use a
cn=James
fraction 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 and
more may be added, but at the same relatively small proportion of total
James
directory entries. Eventually, the
but it will still be a list that is necessary for search performance. If your directory
grows large enough that so many
threshold is met, then the
Every time you search for
single entry in the directory in response to the search request.
When the database grows large, the All IDs threshold will be set for a large
percentage of all index keys and your search performance will significantly
degrade.
.
James
attribute is easy to maintain because only small
cn
filter will be improved because only that small
cn=James
cn=James
entry ID list is replaced with an All IDs token.
cn=James
, the Directory Server will examine every
cn=James
index is
cn cn=James
. Performance for
cn=James
entry ID list can become quite large,
entries are added that the All IDs
Chapter 10
Managing Indexes
. The
Managing Indexes 391