Ubuntu Manpage: slapd-bdb, slapd-hdb - Berkeley DB backends to slapd

Provided by: slapd_2.4.49+dfsg-2ubuntu1.10_amd64

NAME

       slapd-bdb, slapd-hdb - Berkeley DB backends to slapd

SYNOPSIS

       /etc/ldap/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.

       Note that BDB is deprecated and support will be dropped in future OpenLDAP releases. Installations should
       use the mdb backend instead.

       hdb 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 precedence.

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 database options are described in the slapd.conf(5) manual page.

cachesize <integer>
Specify the size in entries of the in-memory entry cache maintained 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> 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.

checksum
Enable checksum validation of DB pages whenever they are read from disk. This setting can only be
configured before any database 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 maximum 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 database and associated indexes live. A
separate directory must be specified for each database. The default is /var/lib/ldap.

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 performance, 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 idlcachesize 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 performance, 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 background 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
individually, 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 evaluation. 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 particular 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/ldap/slapd.conf
              default slapd configuration file

       DB_CONFIG
              Berkeley DB configuration file

ACKNOWLEDGEMENTS

       OpenLDAP  Software  is  developed  and  maintained  by  The  OpenLDAP Project <http://www.openldap.org/>.
       OpenLDAP Software is derived from the University 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                                           2020/01/30                                       SLAPD-BDB(5)