SLAPD-BDB(5)SLAPD-BDB(5)NAME
slapd-bdb, slapd-hdb - Berkeley DB backends to slapd
SYNOPSIS
/etc/openldap/slapd.conf
DESCRIPTION
The bdb backend to slapd(8) uses the Oracle Berkeley DB (BDB) package
to store data. It makes extensive use of indexing and caching to speed
data access.
hdb is the recommended primary database backend. It is a variant of
the bdb backend that uses a hierarchical database layout which supports
subtree renames. It is both more space-efficient and more execution-
efficient than the bdb backend. It is otherwise identical to the bdb
behavior, and all the same configuration options apply.
It is noted that these options are intended to complement Berkeley DB
configuration options set in the environment's DB_CONFIG file. See
Berkeley DB documentation for details on DB_CONFIG configuration
options. Where there is overlap, settings in DB_CONFIG take prece‐
dence.
CONFIGURATION
These slapd.conf options apply to the bdb and hdb backend database.
That is, they must follow a "database bdb" or "database hdb" line and
come before any subsequent "backend" or "database" lines. Other data‐
base options are described in the slapd.conf(5) manual page.
cachesize <integer>
Specify the size in entries of the in-memory entry cache main‐
tained by the bdb or hdb backend database instance. The default
is 1000 entries.
cachefree <integer>
Specify the number of entries to free from the entry cache when
the cache reaches the cachesize limit. The default is 1 entry.
checkpoint <kbyte> <min>
Specify the frequency for checkpointing the database 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> min‐
utes 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> min‐
utes to perform the checkpoint. See the Berkeley DB reference
guide for more details.
checksum
Enable checksum validation of DB pages whenever they are read
from disk. This setting can only be configured before any data‐
base files are created.
cryptfile <file>
Specify the pathname of a file containing an encryption key to
use for encrypting the database. Encryption is performed using
Berkeley DB's implementation of AES. Note that encryption can
only be configured before any database files are created, and
changing the key can only be done after destroying the current
database and recreating it. Encryption is not enabled by
default, and some distributions of Berkeley DB do not support
encryption.
cryptkey <key>
Specify an encryption key to use for encrypting the database.
This option may be used when a separate cryptfile is not
desired. Only one of cryptkey or cryptfile may be configured.
dbconfig <Berkeley-DB-setting>
Specify a configuration directive to be placed in the DB_CONFIG
file of the database directory. The dbconfig directive is just a
convenience to allow all necessary configuration to be set in
the slapd.conf file. The options set using this directive will
only be written to the DB_CONFIG file if no such file existed at
server startup time, otherwise they are completely ignored. This
allows one to set initial values without overwriting/destroying
a DB_CONFIG file that was already customized through other
means. This directive may be specified multiple times, as
needed. For example:
dbconfig set_cachesize 0 1048576 0
dbconfig set_lg_bsize 2097152
dbnosync
Specify that on-disk database contents should not be immediately
synchronized with in memory changes. Enabling this option may
improve performance at the expense of data security. See the
Berkeley DB reference guide for more details.
dbpagesize <dbfile> <size>
Specify the page size to use for a particular database file, in
units of 1024 bytes. The default for the id2entry file is 16,
the default for all other files depends on the size of the
underlying filesystem's block size (typically 4 or 8). The max‐
imum that BerkeleyDB supports is 64. This setting usually should
not need to be changed, but if BerkeleyDB's "db_stat -d" shows a
large amount of overflow pages in use in a file, setting a
larger size may increase performance at the expense of data
integrity. This setting only takes effect when a database is
being newly created. See the Berkeley DB reference guide for
more details.
directory <directory>
Specify the directory where the BDB files containing this data‐
base and associated indexes live. A separate directory must be
specified for each database. The default is
/var/run/slapd/openldap-data.
dirtyread
Allow reads of modified but not yet committed data. Usually
transactions are isolated to prevent other operations from
accessing uncommitted data. This option may improve perfor‐
mance, but may also return inconsistent results if the data
comes from a transaction that is later aborted. In this case,
the modified data is discarded and a subsequent search will
return a different result.
dncachesize <integer>
Specify the maximum number of DNs in the in-memory DN cache.
Ideally this cache should be large enough to contain the DNs of
every entry in the database. If set to a smaller value than the
cachesize it will be silently increased to equal the cachesize.
The default value is 0 which means unlimited, i.e. the DN cache
will grow without bound.
It should be noted that the DN cache is allowed to temporarily
grow beyond the configured size. It does this if many entries
are locked when it tries to do a purge, because that means
they're legitimately in use. Also, the DN cache never purges
entries that have cached children, so depending on the shape of
the DIT, it could have lots of cached DNs over the defined
limit.
idlcachesize <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. An hdb database needs a large idl‐
cachesize for good search performance, typically three times the
cachesize (entry cache size) or larger.
index {<attrlist>|default} [pres,eq,approx,sub,<special>]
Specify the indexes to maintain for the given attribute (or list
of attributes). Some attributes only support a subset of
indexes. If only an <attr> is given, the indices specified for
default are maintained. Note that setting a default does not
imply that all attributes will be indexed. Also, for best per‐
formance, an eq index should always be configured for the
objectClass attribute.
A number of special index parameters may be specified. The
index type sub can be decomposed into subinitial, subany, and
subfinal indices. The special type nolang may be specified to
disallow use of this index by language subtypes. The special
type nosubtypes may be specified to disallow use of this index
by named subtypes. Note: changing index settings in
slapd.conf(5) requires rebuilding indices, see slapindex(8);
changing index settings dynamically by LDAPModifying "cn=config"
automatically causes rebuilding of the indices online in a back‐
ground task.
linearindex
Tell slapindex to index one attribute at a time. By default, all
indexed attributes in an entry are processed at the same time.
With this option, each indexed attribute is processed individu‐
ally, using multiple passes through the entire database. This
option improves slapindex performance when the database size
exceeds the dbcache size. When the dbcache 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.
lockdetect {oldest|youngest|fewest|random|default}
Specify which transaction to abort when a deadlock is detected.
The default is random.
mode <integer>
Specify the file protection mode that newly created database
index files should have. The default is 0600.
searchstack <depth>
Specify the depth of the stack used for search filter evalua‐
tion. Search filters are evaluated on a stack to accommodate
nested AND / OR clauses. An individual stack is assigned to 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 par‐
ticular search operation. These 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
stack uses 512K bytes per level. The default stack depth is 16,
thus 8MB per thread is used.
shm_key <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.
ACCESS CONTROL
The bdb and hdb backends honor access control semantics as indicated in
slapd.access(5).
FILES
/etc/openldap/slapd.conf
default slapd configuration file
DB_CONFIG
Berkeley DB configuration file
SEE ALSOslapd.conf(5), slapd-config(5), slapd(8), slapadd(8), slapcat(8),
slapindex(8), Berkeley DB documentation.
ACKNOWLEDGEMENTS
OpenLDAP Software is developed and maintained by The OpenLDAP Project
<http://www.openldap.org/>. OpenLDAP Software is derived from Univer‐
sity of Michigan LDAP 3.3 Release. Originally begun by Kurt Zeilenga.
Caching mechanisms originally designed by Jong-Hyuk Choi. Completion
and subsequent work, as well as back-hdb, by Howard Chu.
OpenLDAP 2.4.26 2011/06/30 SLAPD-BDB(5)
