# $OpenLDAP: pkg/openldap-guide/admin/slapdconf2.sdf,v 1.20.2.12 2008/04/14 22:37:01 quanah Exp $
# Copyright 2005-2008 The OpenLDAP Foundation, All Rights Reserved.
# COPYING RESTRICTIONS APPLY, see COPYRIGHT.

H1: Configuring slapd

Once the software has been built and installed, you are ready
to configure {{slapd}}(8) for use at your site. Unlike previous
OpenLDAP releases, the slapd(8) runtime configuration in 2.3 (and later)
is fully LDAP-enabled and can be managed using the standard LDAP
operations with data in {{TERM:LDIF}}. The LDAP configuration engine
allows all of slapd's configuration options to be changed on the fly,
generally without requiring a server restart for the changes
to take effect. The old style {{slapd.conf}}(5) file is still
supported, but must be converted to the new {{slapd-config}}(5) format
to allow runtime changes to be saved. While the old style
configuration uses a single file, normally installed as
{{F:/usr/local/etc/openldap/slapd.conf}}, the new style
uses a slapd backend database to store the configuration. The
configuration database normally resides in the
{{F:/usr/local/etc/openldap/slapd.d}} directory. When
converting from the slapd.conf format to slapd.d format, any
include files will also be integrated into the resulting configuration
database.

An alternate configuration directory (or file) can be specified via
a command-line option to {{slapd}}(8). This chapter describes the
general format of the configuration system, followed by a detailed
description of commonly used config settings.

Note: some of the backends and of the distributed overlays
do not support runtime configuration yet.  In those cases,
the old style {{slapd.conf}}(5) file must be used.


H2: Configuration Layout

The slapd configuration is stored as a special LDAP directory with
a predefined schema and DIT. There are specific objectClasses used to
carry global configuration options, schema definitions, backend and
database definitions, and assorted other items. A sample config tree
is shown in Figure 5.1.

!import "config_dit.png"; align="center"; title="Sample configuration tree"
FT[align="Center"] Figure 5.1: Sample configuration tree.

Other objects may be part of the configuration but were omitted from
the illustration for clarity.

The {{slapd-config}} configuration tree has a very specific structure. The
root of the tree is named {{EX:cn=config}} and contains global configuration
settings. Additional settings are contained in separate child entries:
* Dynamically loaded modules
.. These may only be used if the {{EX:--enable-modules}} option was
used to configure the software.
* Schema definitions
.. The {{EX:cn=schema,cn=config}} entry contains the system schema (all
the schema that is hard-coded in slapd).
.. Child entries of {{EX:cn=schema,cn=config}} contain user schema as
loaded from config files or added at runtime.
* Backend-specific configuration 
* Database-specific configuration
.. Overlays are defined in children of the Database entry.
.. Databases and Overlays may also have other miscellaneous children.

The usual rules for LDIF files apply to the configuration information:
Comment lines beginning with a '{{EX:#}}' character
are ignored.  If a line begins with a single space, it is considered a
continuation of the previous line (even if the previous line is a
comment) and the single leading space is removed. Entries are separated by blank lines.

The general layout of the config LDIF is as follows:

>	# global configuration settings
>	dn: cn=config
>	objectClass: olcGlobal
>	cn: config
>	<global config settings>
>
>	# schema definitions
>	dn: cn=schema,cn=config
>	objectClass: olcSchemaConfig
>	cn: schema
>	<system schema>
>
>	dn: cn={X}core,cn=schema,cn=config
>	objectClass: olcSchemaConfig
>	cn: {X}core
>	<core schema>
>
>	# additional user-specified schema
>	...
>
>	# backend definitions
>	dn: olcBackend=<typeA>,cn=config
>	objectClass: olcBackendConfig
>	olcBackend: <typeA>
>	<backend-specific settings>
>
>	# database definitions
>	dn: olcDatabase={X}<typeA>,cn=config
>	objectClass: olcDatabaseConfig
>	olcDatabase: {X}<typeA>
>	<database-specific settings>
>
>	# subsequent definitions and settings
>	...

Some of the entries listed above have a numeric index {{EX:"{X}"}} in
their names. While most configuration settings have an inherent ordering
dependency (i.e., one setting must take effect before a subsequent one
may be set), LDAP databases are inherently unordered. The numeric index
is used to enforce a consistent ordering in the configuration database,
so that all ordering dependencies are preserved. In most cases the index
does not have to be provided; it will be automatically generated based
on the order in which entries are created.

Configuration directives are specified as values of individual
attributes.
Most of the attributes and objectClasses used in the slapd
configuration have a prefix of {{EX:"olc"}} (OpenLDAP Configuration)
in their names. Generally there is a one-to-one correspondence
between the attributes and the old-style {{EX:slapd.conf}} configuration
keywords, using the keyword as the attribute name, with the "olc"
prefix attached.

A configuration directive may take arguments.  If so, the arguments are
separated by white space.  If an argument contains white space,
the argument should be enclosed in double quotes {{EX:"like this"}}.
In the descriptions that follow, arguments that should be replaced
by actual text are shown in brackets {{EX:<>}}.

The distribution contains an example configuration file that will
be installed in the {{F: /usr/local/etc/openldap}} directory.
A number of files containing schema definitions (attribute types
and object classes) are also provided in the
{{F: /usr/local/etc/openldap/schema}} directory.


H2: Configuration Directives

This section details commonly used configuration directives.  For
a complete list, see the {{slapd-config}}(5) manual page.  This section
will treat the configuration directives in a top-down order, starting
with the global directives in the {{EX:cn=config}} entry. Each
directive will be described along with its default value (if any) and
an example of its use.


H3: cn=config

Directives contained in this entry generally apply to the server as a whole.
Most of them are system or connection oriented, not database related. This
entry must have the {{EX:olcGlobal}} objectClass.


H4: olcIdleTimeout: <integer>

Specify the number of seconds to wait before forcibly closing
an idle client connection.  A value of 0, the default,
disables this feature.


H4: olcLogLevel: <level>

This directive specifies the level at which debugging statements
and operation statistics should be syslogged (currently logged to
the {{syslogd}}(8) {{EX:LOG_LOCAL4}} facility). You must have
configured OpenLDAP {{EX:--enable-debug}} (the default) for this
to work (except for the two statistics levels, which are always
enabled). Log levels may be specified as integers or by keyword.
Multiple log levels may be used and the levels are additive.
To display what levels
correspond to what kind of debugging, invoke slapd with {{EX:-?}}
or consult the table below. The possible values for <level> are:

!block table; colaligns="RL"; align=Center; \
	title="Table 5.1: Debugging Levels"
Level	Keyword	Description
-1	Any	enable all debugging
0		no debugging
1	Trace	trace function calls
2	Packets	debug packet handling
4	Args	heavy trace debugging
8	Conns	connection management
16	BER	print out packets sent and received
32	Filter	search filter processing
64	Config	configuration processing
128	ACL	access control list processing
256	Stats	stats log connections/operations/results
512	Stats2	stats log entries sent
1024	Shell	print communication with shell backends
2048	Parse	print entry parsing debugging
4096	Cache	database cache processing
8192	Index	database indexing
16384	Sync	syncrepl consumer processing
!endblock

\Example:

E: olcLogLevel: -1

This will cause lots and lots of debugging information to be
logged.

E: olcLogLevel: Conns Filter

Just log the connection and search filter processing.

\Default:

E: olcLogLevel: Stats


H4: olcReferral <URI>

This directive specifies the referral to pass back when slapd
cannot find a local database to handle a request.

\Example:

>	olcReferral: ldap://root.openldap.org

This will refer non-local queries to the global root LDAP server
at the OpenLDAP Project. Smart LDAP clients can re-ask their
query at that server, but note that most of these clients are
only going to know how to handle simple LDAP URLs that
contain a host part and optionally a distinguished name part.


H4: Sample Entry

>dn: cn=config
>objectClass: olcGlobal
>cn: config
>olcIdleTimeout: 30
>olcLogLevel: Stats
>olcReferral: ldap://root.openldap.org


H3: cn=module

If support for dynamically loaded modules was enabled when configuring
slapd, {{EX:cn=module}} entries may be used to specify sets of modules to load.
Module entries must have the {{EX:olcModuleList}} objectClass.


H4: olcModuleLoad: <filename>

Specify the name of a dynamically loadable module to load. The filename
may be an absolute path name or a simple filename. Non-absolute names
are searched for in the directories specified by the {{EX:olcModulePath}}
directive.


H4: olcModulePath: <pathspec>

Specify a list of directories to search for loadable modules. Typically the
path is colon-separated but this depends on the operating system.


H4: Sample Entries

>dn: cn=module{0},cn=config
>objectClass: olcModuleList
>cn: module{0}
>olcModuleLoad: /usr/local/lib/smbk5pwd.la
>
>dn: cn=module{1},cn=config
>objectClass: olcModuleList
>cn: module{1}
>olcModulePath: /usr/local/lib:/usr/local/lib/slapd
>olcModuleLoad: accesslog.la
>olcModuleLoad: pcache.la


H3: cn=schema

The cn=schema entry holds all of the schema definitions that are hard-coded
in slapd. As such, the values in this entry are generated by slapd so no
schema values need to be provided in the config file. The entry must still
be defined though, to serve as a base for the user-defined schema to add
in underneath. Schema entries must have the {{EX:olcSchemaConfig}}
objectClass.


H4: olcAttributeTypes: <{{REF:RFC4512}} Attribute Type Description>

This directive defines an attribute type.
Please see the {{SECT:Schema Specification}} chapter
for information regarding how to use this directive.


H4: olcObjectClasses: <{{REF:RFC4512}} Object Class Description>

This directive defines an object class.
Please see the {{SECT:Schema Specification}} chapter for
information regarding how to use this directive.


H4: Sample Entries

>dn: cn=schema,cn=config
>objectClass: olcSchemaConfig
>cn: schema
>
>dn: cn=test,cn=schema,cn=config
>objectClass: olcSchemaConfig
>cn: test
>olcAttributeTypes: ( 1.1.1
>  NAME 'testAttr'
>  EQUALITY integerMatch
>  SYNTAX 1.3.6.1.4.1.1466.115.121.1.27 )
>olcAttributeTypes: ( 1.1.2 NAME 'testTwo' EQUALITY caseIgnoreMatch
>  SUBSTR caseIgnoreSubstringsMatch SYNTAX 1.3.6.1.4.1.1466.115.121.1.44 )
>olcObjectClasses: ( 1.1.3 NAME 'testObject'
>  MAY ( testAttr $ testTwo ) AUXILIARY )


H3: Backend-specific Directives

Backend directives apply to all database instances of the
same type and, depending on the directive, may be overridden
by database directives. Backend entries must have the
{{EX:olcBackendConfig}} objectClass.

H4: olcBackend: <type>

This directive names a backend-specific configuration entry.
{{EX:<type>}} should be one of the
supported backend types listed in Table 5.2.

!block table; align=Center; coltags="EX,N"; \
	title="Table 5.2: Database Backends"
Types	Description
bdb	Berkeley DB transactional backend
config	Slapd configuration backend
dnssrv	DNS SRV backend
hdb	Hierarchical variant of bdb backend
ldap	Lightweight Directory Access Protocol (Proxy) backend
ldif	Lightweight Data Interchange Format backend
meta	Meta Directory backend
monitor	Monitor backend
passwd	Provides read-only access to {{passwd}}(5)
perl	Perl Programmable backend
shell	Shell (extern program) backend
sql	SQL Programmable backend
!endblock

\Example:

>	olcBackend: bdb

There are no other directives defined for this entry.  Specific backend
types may define additional attributes for their particular use but so
far none have ever been defined.  As such, these directives usually do
not appear in any actual configurations.


H4: Sample Entry

> dn: olcBackend=bdb,cn=config
> objectClass: olcBackendConfig
> olcBackend: bdb


H3: Database-specific Directives

Directives in this section are supported by every type of database.
Database entries must have the {{EX:olcDatabaseConfig}} objectClass.

H4: olcDatabase: [{<index>}]<type>

This directive names a specific database instance. The numeric {<index>} may
be provided to distinguish multiple databases of the same type. Usually the
index can be omitted, and slapd will generate it automatically.
{{EX:<type>}} should be one of the
supported backend types listed in Table 5.2 or the {{EX:frontend}} type.

The {{EX:frontend}} is a special database that is used to hold
database-level options that should be applied to all the other
databases. Subsequent database definitions may also override some
frontend settings.

The {{EX:config}} database is also special; both the {{EX:config}} and
the {{EX:frontend}} databases are always created implicitly even if they
are not explicitly configured, and they are created before any other
databases.

\Example:

>	olcDatabase: bdb

This marks the beginning of a new {{TERM:BDB}} database instance.


H4: olcAccess: to <what> [ by <who> [<accesslevel>] [<control>] ]+

This directive grants access (specified by <accesslevel>) to a
set of entries and/or attributes (specified by <what>) by one or
more requestors (specified by <who>).
See the {{SECT:Access Control}} section of this guide for basic usage.

!if 0
More detailed discussion of this directive can be found in the
{{SECT:Advanced Access Control}} chapter.
!endif

Note: If no {{EX:olcAccess}} directives are specified, the default
access control policy, {{EX:to * by * read}}, allows all
users (both authenticated and anonymous) read access.

Note: Access controls defined in the frontend are appended to all
other databases' controls.


H4: olcReadonly { TRUE | FALSE }

This directive puts the database into "read-only" mode. Any
attempts to modify the database will return an "unwilling to
perform" error.

\Default:

>	olcReadonly: FALSE


H4: olcRootDN: <DN>

This directive specifies the DN that is not subject to
access control or administrative limit restrictions for
operations on this database.  The DN need not refer to
an entry in this database or even in the directory. The
DN may refer to a SASL identity.

Entry-based Example:

>	olcRootDN: "cn=Manager,dc=example,dc=com"

SASL-based Example:

>	olcRootDN: "uid=root,cn=example.com,cn=digest-md5,cn=auth"

See the {{SECT:SASL Authentication}} section for information on
SASL authentication identities.


H4: olcRootPW: <password>

This directive can be used to specify a password for the DN for
the rootdn (when the rootdn is set to a DN within the database).

\Example:

>	olcRootPW: secret

It is also permissible to provide a hash of the password in
{{REF:RFC2307}} form.  {{slappasswd}}(8) may be used to generate
the password hash.

\Example:

>	olcRootPW: {SSHA}ZKKuqbEKJfKSXhUbHG3fG8MDn9j1v4QN

The hash was generated using the command {{EX:slappasswd -s secret}}.


H4: olcSizeLimit: <integer>

This directive specifies the maximum number of entries to return
from a search operation.

\Default:

>	olcSizeLimit: 500



H4: olcSuffix: <dn suffix>

This directive specifies the DN suffix of queries that will be
passed to this backend database. Multiple suffix lines can be
given, and usually at least one is required for each database
definition. (Some backend types, such as {{EX:frontend}} and
{{EX:monitor}} use a hard-coded suffix which may not be overridden
in the configuration.)

\Example:

>	olcSuffix: "dc=example,dc=com"

Queries with a DN ending in "dc=example,dc=com"
will be passed to this backend.

Note: When the backend to pass a query to is selected, slapd
looks at the suffix value(s) in each database definition in the
order in which they were configured. Thus, if one database suffix is a
prefix of another, it must appear after it in the configuration.


H4: olcSyncrepl

>	olcSyncrepl: rid=<replica ID>
>		provider=ldap[s]://<hostname>[:port]
>		[type=refreshOnly|refreshAndPersist]
>		[interval=dd:hh:mm:ss]
>		[retry=[<retry interval> <# of retries>]+]
>		searchbase=<base DN>
>		[filter=<filter str>]
>		[scope=sub|one|base]
>		[attrs=<attr list>]
>		[attrsonly]
>		[sizelimit=<limit>]
>		[timelimit=<limit>]
>		[schemachecking=on|off]
>		[bindmethod=simple|sasl]
>		[binddn=<DN>]
>		[saslmech=<mech>]
>		[authcid=<identity>]
>		[authzid=<identity>]
>		[credentials=<passwd>]
>		[realm=<realm>]
>		[secprops=<properties>]
>		[starttls=yes|critical]
>		[tls_cert=<file>]
>		[tls_key=<file>]
>		[tls_cacert=<file>]
>		[tls_cacertdir=<path>]
>		[tls_reqcert=never|allow|try|demand]
>		[tls_ciphersuite=<ciphers>]
>		[tls_crlcheck=none|peer|all]
>		[logbase=<base DN>]
>		[logfilter=<filter str>]
>		[syncdata=default|accesslog|changelog]


This directive specifies the current database as a replica of the
master content by establishing the current {{slapd}}(8) as a
replication consumer site running a syncrepl replication engine.
The master database is located at the replication provider site
specified by the {{EX:provider}} parameter. The replica database is
kept up-to-date with the master content using the LDAP Content
Synchronization protocol. See {{REF:RFC4533}}
for more information on the protocol.

The {{EX:rid}} parameter is used for identification of the current
{{EX:syncrepl}} directive within the replication consumer server,
where {{EX:<replica ID>}} uniquely identifies the syncrepl specification
described by the current {{EX:syncrepl}} directive. {{EX:<replica ID>}}
is non-negative and is no more than three decimal digits in length.

The {{EX:provider}} parameter specifies the replication provider site
containing the master content as an LDAP URI. The {{EX:provider}}
parameter specifies a scheme, a host and optionally a port where the
provider slapd instance can be found. Either a domain name or IP
address may be used for <hostname>. Examples are
{{EX:ldap://provider.example.com:389}} or {{EX:ldaps://192.168.1.1:636}}.
If <port> is not given, the standard LDAP port number (389 or 636) is used.
Note that the syncrepl uses a consumer-initiated protocol, and hence its
specification is located at the consumer site, whereas the {{EX:replica}}
specification is located at the provider site. {{EX:syncrepl}} and
{{EX:replica}} directives define two independent replication
mechanisms. They do not represent the replication peers of each other.

The content of the syncrepl replica is defined using a search
specification as its result set. The consumer slapd will
send search requests to the provider slapd according to the search
specification. The search specification includes {{EX:searchbase}},
{{EX:scope}}, {{EX:filter}}, {{EX:attrs}}, {{EX:attrsonly}},
{{EX:sizelimit}}, and {{EX:timelimit}} parameters as in the normal
search specification. The {{EX:searchbase}} parameter has no
default value and must always be specified. The {{EX:scope}} defaults
to {{EX:sub}}, the {{EX:filter}} defaults to {{EX:(objectclass=*)}},
{{EX:attrs}} defaults to {{EX:"*,+"}} to replicate all user and operational
attributes, and {{EX:attrsonly}} is unset by default. Both {{EX:sizelimit}}
and {{EX:timelimit}} default to "unlimited", and only positive integers
or "unlimited" may be specified.

The {{TERM[expand]LDAP Sync}} protocol has two operation
types: {{EX:refreshOnly}} and {{EX:refreshAndPersist}}.
The operation type is specified by the {{EX:type}} parameter.
In the {{EX:refreshOnly}} operation, the next synchronization search operation
is periodically rescheduled at an interval time after each
synchronization operation finishes. The interval is specified
by the {{EX:interval}} parameter. It is set to one day by default.
In the {{EX:refreshAndPersist}} operation, a synchronization search
remains persistent in the provider {{slapd}} instance. Further updates to the
master replica will generate {{EX:searchResultEntry}} to the consumer slapd
as the search responses to the persistent synchronization search.

If an error occurs during replication, the consumer will attempt to reconnect
according to the retry parameter which is a list of the <retry interval>
and <# of retries> pairs. For example, retry="60 10 300 3" lets the consumer
retry every 60 seconds for the first 10 times and then retry every 300 seconds
for the next three times before stop retrying. + in <#  of retries> means
indefinite number of retries until success.

The schema checking can be enforced at the LDAP Sync consumer site
by turning on the {{EX:schemachecking}} parameter.
If it is turned on, every replicated entry will be checked for its
schema as the entry is stored into the replica content.
Every entry in the replica should contain those attributes
required by the schema definition.
If it is turned off, entries will be stored without checking
schema conformance. The default is off.

The {{EX:binddn}} parameter gives the DN to bind as for the
syncrepl searches to the provider slapd. It should be a DN
which has read access to the replication content in the
master database. 

The {{EX:bindmethod}} is {{EX:simple}} or {{EX:sasl}},
depending on whether simple password-based authentication or
{{TERM:SASL}} authentication is to be used when connecting
to the provider {{slapd}} instance.

Simple authentication should not be used unless adequate data
integrity and confidentiality protections are in place (e.g. TLS
or IPsec). Simple authentication requires specification of {{EX:binddn}}
and {{EX:credentials}} parameters.

SASL authentication is generally recommended.  SASL authentication
requires specification of a mechanism using the {{EX:saslmech}} parameter.
Depending on the mechanism, an authentication identity and/or
credentials can be specified using {{EX:authcid}} and {{EX:credentials}},
respectively.  The {{EX:authzid}} parameter may be used to specify
an authorization identity.

The {{EX:realm}} parameter specifies a realm which a certain
mechanisms authenticate the identity within. The {{EX:secprops}}
parameter specifies Cyrus SASL security properties.

The {{EX:starttls}} parameter specifies use of the StartTLS extended
operation to establish a TLS session before authenticating to the provider.
If the {{EX:critical}} argument is supplied, the session will be aborted
if the StartTLS request fails.  Otherwise the syncrepl session continues
without TLS.  Note that the main slapd TLS settings are not used by the
syncrepl engine; by default the TLS parameters from a {{ldap.conf}}(5)
configuration file will be used.  TLS settings may be specified here,
in which case any {{ldap.conf}}(5) settings will be completely ignored.

Rather than replicating whole entries, the consumer can query logs
of data modifications.  This mode of operation is referred to as
{{delta syncrepl}}.  In addition to the above parameters, the
{{EX:logbase}} and {{EX:logfilter}} parameters must be set appropriately
for the log that will be used. The {{EX:syncdata}} parameter must
be set to either {{EX:"accesslog"}} if the log conforms to the
{{slapo-accesslog}}(5) log format, or {{EX:"changelog"}} if the log
conforms to the obsolete {{changelog}} format. If the {{EX:syncdata}}
parameter is omitted or set to {{EX:"default"}} then the log
parameters are ignored.

The {{syncrepl}} replication mechanism is supported by the {{bdb}} and
{{hdb}} backends.

See the {{SECT:LDAP Sync Replication}} chapter of this guide for
more information on how to use this directive.


H4: olcTimeLimit: <integer>

This directive specifies the maximum number of seconds (in real
time) slapd will spend answering a search request. If a
request is not finished in this time, a result indicating an
exceeded timelimit will be returned.

\Default:

>	olcTimeLimit: 3600


H4: olcUpdateref: <URL>

This directive is only applicable in a slave slapd. It
specifies the URL to return to clients which submit update
requests upon the replica.
If specified multiple times, each {{TERM:URL}} is provided.

\Example:

>	olcUpdateref:	ldap://master.example.net


H4: Sample Entries

>dn: olcDatabase=frontend,cn=config
>objectClass: olcDatabaseConfig
>objectClass: olcFrontendConfig
>olcDatabase: frontend
>olcReadOnly: FALSE
>
>dn: olcDatabase=config,cn=config
>objectClass: olcDatabaseConfig
>olcDatabase: config
>olcRootDN: cn=Manager,dc=example,dc=com


H3: BDB and HDB Database Directives

Directives in this category apply to both the {{TERM:BDB}}
and the {{TERM:HDB}} database.
They are used in an olcDatabase entry in addition to the generic
database directives defined above.  For a complete reference
of BDB/HDB configuration directives, see {{slapd-bdb}}(5). In
addition to the {{EX:olcDatabaseConfig}} objectClass, BDB and HDB
database entries must have the {{EX:olcBdbConfig}} and
{{EX:olcHdbConfig}} objectClass, respectively.


H4: olcDbDirectory: <directory>

This directive specifies the directory where the BDB files
containing the database and associated indices live.

\Default:

>	olcDbDirectory: /usr/local/var/openldap-data


H4: olcDbCachesize: <integer>

This directive specifies the size in entries of the in-memory
cache maintained by the BDB backend database instance.

\Default:

>	olcDbCachesize: 1000


H4: olcDbCheckpoint: <kbyte> <min>

This directive specifies how often to checkpoint the BDB transaction log.
A checkpoint operation flushes the database buffers to disk and writes a
checkpoint record in the log.
The checkpoint will occur if either <kbyte> data has been written or
<min> minutes have passed since the last checkpoint. Both arguments default
to zero, in which case they are ignored. When the <min> argument is
non-zero, an internal task will run every <min> minutes to perform the
checkpoint. See the Berkeley DB reference guide for more details.

\Example:

>	olcDbCheckpoint: 1024 10


H4: olcDbConfig: <DB_CONFIG setting>

This attribute specifies a configuration directive to be placed in the
{{EX:DB_CONFIG}} file of the database directory. At server startup time, if
no such file exists yet, the {{EX:DB_CONFIG}} file will be created and the
settings in this attribute will be written to it. If the file exists,
its contents will be read and displayed in this attribute. The attribute
is multi-valued, to accommodate multiple configuration directives. No default
is provided, but it is essential to use proper settings here to get the
best server performance.

Any changes made to this attribute will be written to the {{EX:DB_CONFIG}}
file and will cause the database environment to be reset so the changes
can take immediate effect. If the environment cache is large and has not
been recently checkpointed, this reset operation may take a long time. It
may be advisable to manually perform a single checkpoint using the Berkeley DB
{{db_checkpoint}} utility before using LDAP Modify to change this
attribute.

\Example:

>	olcDbConfig: set_cachesize 0 10485760 0
>	olcDbConfig: set_lg_bsize 2097512
>	olcDbConfig: set_lg_dir /var/tmp/bdb-log
>	olcDbConfig: set_flags DB_LOG_AUTOREMOVE

In this example, the BDB cache is set to 10MB, the BDB transaction log
buffer size is set to 2MB, and the transaction log files are to be stored
in the /var/tmp/bdb-log directory. Also a flag is set to tell BDB to
delete transaction log files as soon as their contents have been
checkpointed and they are no longer needed. Without this setting the
transaction log files will continue to accumulate until some other
cleanup procedure removes them. See the Berkeley DB documentation for the
{{EX:db_archive}} command for details. For a complete list of Berkeley DB 
flags please see - {{URL:http://www.oracle.com/technology/documentation/berkeley-db/db/api_c/env_set_flags.html}}

Ideally the BDB cache must be
at least as large as the working set of the database, the log buffer size
should be large enough to accommodate most transactions without overflowing,
and the log directory must be on a separate physical disk from the main
database files. And both the database directory and the log directory
should be separate from disks used for regular system activities such as
the root, boot, or swap filesystems. See the FAQ-o-Matic and the Berkeley DB
documentation for more details.


H4: olcDbNosync: { TRUE | FALSE }

This option causes on-disk database contents to not be immediately
synchronized with in memory changes upon change.  Setting this option
to {{EX:TRUE}} may improve performance at the expense of data integrity. This
directive has the same effect as using
>	olcDbConfig: set_flags DB_TXN_NOSYNC


H4: olcDbIDLcacheSize: <integer>

Specify the size of the in-memory index cache, in index slots. The
default is zero. A larger value will speed up frequent searches of
indexed entries. The optimal size will depend on the data and search
characteristics of the database, but using a number three times
the entry cache size is a good starting point.

\Example:

>	olcDbIDLcacheSize: 3000


H4: olcDbIndex: {<attrlist> | default} [pres,eq,approx,sub,none]

This directive specifies the indices to maintain for the given
attribute. If only an {{EX:<attrlist>}} is given, the default
indices are maintained. The index keywords correspond to the
common types of matches that may be used in an LDAP search filter.

\Example:

>	olcDbIndex: default pres,eq
>	olcDbIndex: uid
>	olcDbIndex: cn,sn pres,eq,sub
>	olcDbIndex: objectClass eq

The first line sets the default set of indices to maintain to
present and equality.  The second line causes the default (pres,eq)
set of indices to be maintained for the {{EX:uid}} attribute type.
The third line causes present, equality, and substring indices to
be maintained for {{EX:cn}} and {{EX:sn}} attribute types.  The
fourth line causes an equality index for the {{EX:objectClass}}
attribute type.

There is no index keyword for inequality matches. Generally these
matches do not use an index. However, some attributes do support
indexing for inequality matches, based on the equality index.

A substring index can be more explicitly specified as {{EX:subinitial}},
{{EX:subany}}, or {{EX:subfinal}}, corresponding to the three 
possible components
of a substring match filter. A subinitial index only indexes
substrings that appear at the beginning of an attribute value.
A subfinal index only indexes substrings that appear at the end
of an attribute value, while subany indexes substrings that occur
anywhere in a value.

Note that by default, setting an index for an attribute also
affects every subtype of that attribute. E.g., setting an equality
index on the {{EX:name}} attribute causes {{EX:cn}}, {{EX:sn}}, and every other
attribute that inherits from {{EX:name}} to be indexed.

By default, no indices are maintained.  It is generally advised
that minimally an equality index upon objectClass be maintained.

>	olcDbindex: objectClass eq

Additional indices should be configured corresponding to the
most common searches that are used on the database.
Presence indexing should not be configured for an attribute
unless the attribute occurs very rarely in the database, and
presence searches on the attribute occur very frequently during
normal use of the directory. Most applications don't use presence
searches, so usually presence indexing is not very useful.

If this setting is changed while slapd is running, an internal task
will be run to generate the changed index data. All server operations
can continue as normal while the indexer does its work.  If slapd is
stopped before the index task completes, indexing will have to be
manually completed using the slapindex tool.


H4: olcDbLinearIndex: { TRUE | FALSE }

If this setting is {{EX:TRUE}} slapindex will index one attribute
at a time. The default settings is {{EX:FALSE}} in which case all
indexed attributes of an entry are processed at the same time. When
enabled, each indexed attribute is processed individually, using
multiple passes through the entire database. This option improves
slapindex performance when the database size exceeds the BDB cache
size. When the BDB cache is large enough, this option is not needed
and will decrease performance. Also by default, slapadd performs
full indexing and so a separate slapindex run is not needed. With
this option, slapadd does no indexing and slapindex must be used.


H4: olcDbMode: <integer>

This directive specifies the file protection mode that newly
created database index files should have.

\Default:

>	olcDbMode: 0600


H4: olcDbSearchStack: <integer>

Specify the depth of the stack used for search filter evaluation.
Search filters are evaluated on a stack to accommodate nested {{EX:AND}} /
{{EX:OR}} clauses. An individual stack is allocated for each server thread.
The depth of the stack determines how complex a filter can be evaluated
without requiring any additional memory allocation. Filters that are
nested deeper than the search stack depth will cause a separate stack to
be allocated for that particular search operation. These separate allocations
can have a major negative impact on server performance, but specifying
too much stack will also consume a great deal of memory. Each search
uses 512K bytes per level on a 32-bit machine, or 1024K bytes per level
on a 64-bit machine. The default stack depth is 16, thus 8MB or 16MB
per thread is used on 32 and 64 bit machines, respectively. Also the
512KB size of a single stack slot is set by a compile-time constant which
may be changed if needed; the code must be recompiled for the change
to take effect.

\Default:

>	olcDbSearchStack: 16


H4: olcDbShmKey: <integer>

Specify a key for a shared memory BDB environment. By default the BDB
environment uses memory mapped files. If a non-zero value is specified,
it will be used as the key to identify a shared memory region that will
house the environment.

\Example:

>	olcDbShmKey: 42


H4: Sample Entry

>dn: olcDatabase=hdb,cn=config
>objectClass: olcDatabaseConfig
>objectClass: olcHdbConfig
>olcDatabase: hdb
>olcSuffix: "dc=example,dc=com"
>olcDbDirectory: /usr/local/var/openldap-data
>olcDbCacheSize: 1000
>olcDbCheckpoint: 1024 10
>olcDbConfig: set_cachesize 0 10485760 0
>olcDbConfig: set_lg_bsize 2097152
>olcDbConfig: set_lg_dir /var/tmp/bdb-log
>olcDbConfig: set_flags DB_LOG_AUTOREMOVE
>olcDbIDLcacheSize: 3000
>olcDbIndex: objectClass eq
