Red Hat DIRECTORY SERVER 8.0, Руководство администратора

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Chapter 15. Tuning Directory Server Performance
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15.2. Tuning Database Performance
This section is divided into the following parts which describe methods for tuning database
performance:
•
Section 15.2.1, “Optimizing Search Performance”
•
Section 15.2.2, “Tuning Transaction Logging”
•
Section 15.2.3, “Changing the Location of the Database Transaction Log”
•
Section 15.2.4, “Changing the Database Checkpoint Interval”
•
Section 15.2.5, “Disabling Durable Transactions”
•
Section 15.2.6, “Specifying Transaction Batching”
15.2.1. Optimizing Search Performance
Improve server performance on searches by tuning database settings. The database attributes that
affect performance mainly define the amount of memory available to the server. There are two kinds
of database caches, one for the default database cache and the other for the entry cache. The server
has one default database cache per server, and one entry cache per database.
To improve the cache hit ratio on search operations, increase the amount of data that the Directory
Server maintains in the database cache. Do this by increasing the cache size. The maximum values
that can be set for these attributes depends on the amount of real memory on the machine. Roughly,
the amount of available memory on the machine should always be greater than sum total of the default
database cache size and sum of each entry cache size.
Use caution when changing these two attributes. The ability to improve server performance with
these attributes depends on the size of the database, the amount of physical memory available on the
machine, and whether directory searches are random (that is, if the directory clients are searching for
random and widely scattered directory data).
If the database does not fit into memory and if searches are random, attempting to increase the values
set on these attributes does not help directory performance. In fact, changing these attributes may
harm overall performance.
The following attributes can be tuned:
• The attributes of the database that manages all other database instances. The Directory Server
Console only shows the databases that contain the directory data and the
NetscapeRoot
database. However, the server uses another database to manage these. On this database, the
following attributes can be changed to improve performance:
• The amount of memory to make available for all databases (maximum cache size).
• The maximum number of entries for the server to verify in response to a search request (look-
through limit).
• The amount of memory to make available for import (import cache size).
• The attributes of each database used to store directory data, including the server configuration
data in the
NetscapeRoot
database. On these databases, to improve performance, configure the
amount of memory to make available for cached entries (memory available for cache).