SLAPD-BDB(5)                  File Formats Manual                 SLAPD-BDB(5)

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


       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

       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

       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.

              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

       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

              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

              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

       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.

              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

       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.

       The bdb and hdb backends honor access control semantics as indicated in

              default slapd configuration file

              Berkeley DB configuration file

       slapd.conf(5), slapd-config(5), slapd-mdb(5), slapd(8), slapadd(8),
       slapcat(8), slapindex(8), Berkeley DB documentation.

       OpenLDAP Software is developed and maintained by The OpenLDAP Project
       <>.  OpenLDAP Software is derived from
       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 2.4.40                   2014/09/20                      SLAPD-BDB(5)