HP-UX Directory Server 8.1 Performance Tuning and Sizing Guidelines

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overridden when the server replaces these values with its own guessed values at a later stage
of the server startup. For more technical information on this attribute, see the cache size
section of the Berkeley DB reference guide.
Attempting to set a value that is not a number or is too big for a 32-bit signed integer returns
an LDAP_UNWILLING_TO_PERFORM error message with additional error information
explaining the problem.
The server has to be restarted for changes to this attribute to take effect.
Entry DN: cn=config,cn=ldbm database,cn=plugins,cn=config
Valid Range: 500KB to 4GB for 32-bit platforms and 500KB to 2^64-1
for 64-bit platforms
Default Value: 10,000,000 bytes
Syntax: Integer
Example: nsslapd-dbcachesize: 10,000,000
The database cache is used by the database to create and manage indexes and perform other
database specific work. The nsslapd-dbcache parameter is set globally for the server and is
shared by all the database backends on the server.
Tuning nsslapd-dbcachesize can be done by following these steps:
Step 1: Set the value of nsslapd-dbcachesize and then start the directory server.
Step 2: Prime the directory by sending the following ldapsearch command (label it as “ldapsearch
command 1”):
#./ldapsearch –b “<root suffix>” –h <host> -p <port> -D
“cn=directory manager” –w passwd “objectclass=*” > /dev/null
Step 3: Check database-related monitoring attributes by sending a different ldapsearch request
(label it as “ldapsearch command 2”):
# ./ldapsearch -p PORT -b "cn=monitor, cn=ldbm database, cn=plugins,
cn=config" –D "cn=directory manager" -w PASSWD “objectclass=*"
|grep dbcache
dbcachehits: 236
dbcachetries: 280
dbcachehitratio: 84
dbcachepagein: 44
dbcachepageout: 0
dbcacheroevict: 0
dbcacherwevict: 0
Step 4: If dbcachepageout, dbcacheroevict, and dbcacherwevict are not equal to zero,
you might want to increase nsslapd-dbcachesize, and repeat steps 1 - 3 until these three
attribute values equal zero, or dbcachesize reaches the maximum value, or dbcachepagein
stops increasing. When nsslapd-dbcachesize is not big enough, pages need to be discarded
from the dbcache to make room for new pages. This is indicated by attributes dbcachepageout,
dbcacheroevict, and dbcacherwevict. For more information about these attributes, see the
HP-UX Directory Server configuration, command, and file reference.
To estimate the amount of RAM needed for an optimized database cache, you can use the following
formula: