Linux Networking Cookbook

12.11. Configuring the Berkeley DB

Problem

You know that you need to use the /var/lib/ldap/DB_CONFIG file to configure the database backend to your LDAP directory (Berkeley DB) so that it will perform peppily and not get all bogged down. How do you know what options and values to use?

Solution

We'll start off with some reasonable values for starters, and then learn how to make some calculations to fine-tune them.

Be sure to check your slapd.conf for duplicate BDB entries and get rid of them. They can go in either file, but it's best to keep them all in DB_CONFIG. You don't want duplicates or conflicting entries.

First, make sure there is a cachesize entry in slapd.conf:

	cachesize 5000

Then, enter these options and values into /var/lib/ldap/DB_CONFIG:

	##/var/lib/ldap/DB_CONFIG
	set_cachesize 0 1048576 0
	set_lk_max_objects 1500
	set_lk_max_locks 1500
	set_lk_max_lockers 1500
	#
	#logging settings
	set_lg_regionmax 1048576
	set_lg_bsize 32768
	set_lg_max 131072
	set_lg_dir /var/log/openldap

The set_cachesize value is in bytes, and must be a power of 2, so the example is one megabyte. How do you know how much to use? Use the db4.2_stat command on Debian, and the db_stat command on Fedora to generate statistics from id2entry.bdb and dn2id.bdb, which are the two main database files:

	# db4.2_stat -d /var/lib/ldap/id2entry.bdb 53162 Btree magic number. 9 Btree version number. Flags: little-endian 2 Minimum keys per-page. 16384 Underlying database page size. 1 Number of levels in the tree. 6 Number of unique ...