6.4. Setting the Size of the DN Cache

The entryrdn index is used to associate DNs and RDNs with entries. It enables the server to efficiently perform subtree rename, entry move, and moddn operations. The DN cache is used to cache the in-memory representation of the entryrdn index to avoid expensive file I/O and transformation operations. For best performance, especially with but not limited to entry rename and move operations, set the DN cache to a size that enables Directory Server to cache all DNs in the database.
If a DN is not stored in the cache, Directory Server reads the DN from the entryrdn.db index database file and converts the DNs from the on-disk format to the in-memory format. DNs that are stored in the cache enable the server to skip the disk I/O and conversion steps.

6.4.1. Setting the Size of the DN Cache Using the Command Line

To set the DN cache size of a database using the command line:
  1. Display the suffixes and their corresponding back end:
    # dsconf -D "cn=Directory Manager" ldap://server.example.com suffix list
    dc=example,dc=com (userroot)
    This command displays the name of the back end database next to each suffix. You require the suffix's database name in the next step.
  2. Use the following command to set the DN cache size:
    # dsconf -D "cn=Directory Manager" ldap://server.example.com backend suffix set --dncache-memsize=20971520 userRoot
    This command sets the DN cache for the userRoot database to 20 megabytes.
  3. Restart the Directory Service instance:
    # dsctl instance_name restart

6.4.2. Setting the Size of the DN Cache Using the Web Console

To set DN cache size of a database using the Web Console:
  1. Open the Directory Server user interface in the web console. For details, see Logging Into Directory Server Using the Web Console section in the Red Hat Directory Server Administration Guide.
  2. Select the instance.
  3. On the Database tab, select the suffix for which you want to set the DN cache size.
  4. Enter the size in bytes into the DN Cache Size (bytes) field.
  5. Click Save Configuration.
  6. Click the Actions button, and select Restart Instance.