Netscape NETSCAPE DIRECTORY SERVER 6.02, Руководство администратора

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Managing Indexes
Chapter 10 Managing Indexes 369
If your directory size is stable, set the All IDs Threshold to about 5 percent of the
total number of entries stored in your directory. That is, if you have 50,000 entries
in your directory, set the All IDs Threshold to 2,500.
If, you plan to add large numbers of entries to your directory in the near future,
you should carefully consider your All IDs Threshold value. Consider the
following:
• Changing the All IDs Threshold means that you have to rebuild your database.
This is a potentially expensive operation, especially for directories that contain
millions of entries.
• While we recommend setting the All IDs Threshold to 5 percent of your
directory size, you should not see serious performance problems if your All
IDs Threshold is as little as 0.5 percent of your current database size or as great
as 50 percent of your current database size. However, we nevertheless
recommend you aim to stay as close to the 5 percent rule as possible.
You need to balance your current directory needs against future expansion plans to
avoid changing the All IDs Threshold at some later stage (which requires a
database rebuild).
Suppose, for example, that your current directory is 50,000 entries in size.
However, in the next few years you expect your directory to grow 1,000,000 entries.
If you set your All IDs Threshold to 5 percent of 50,000 (2,500), then when your
directory grows to 1,000,000 entries you will have a performance problem. 2,500
entries is too low for a database containing 1,000,000 entries because the lower limit
for a 1,000,000 entry database is .5 percent of 1,000,000, i.e.5,000 entries.
If you expect your directory to grow considerably in the future, you can do one of
the following:
• Set the All IDs Threshold to the current best value (2,500), and plan on
rebuilding your database when your directory becomes large enough to
warrant it. A database rebuild means shutting down your directory for
however long the rebuild takes, or at least putting your directory into
read-only mode. It also means reinitializing any consumer servers that your
Directory Server is replicating entries to.
• Find a value that is a bit high for your current needs but that will work well for
your future needs. For example, if your current directory contains 50,000
entries, try setting the All IDs Threshold to 20,000—that is 40 percent of 50,000
(which puts it within range of your current directory needs) and 2 percent of
1,000,000 (which puts it within range of your future directory needs).