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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 exten-sive extensive
       sive 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  configura-tion configuration
       tion 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  cache-size cachesize
              size 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  check-point checkpoint
              point  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 data-base. database.
              base. 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  direc-tory. directory.
              tory.  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  sup-ports supports
              ports  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/db/openldap/openldap-data.

       dirtyread
              Allow reads of modified but not yet committed data.  Usually transactions are isolated to pre-vent prevent
              vent  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 chil-dren, children,
              dren, 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 idlcachesize
              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 speci-fied specified
              fied 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 config-ured configured
              ured 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  dynami-cally dynamically
              cally  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  slapin-dex slapindex
              dex  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, sla-padd slapadd
              padd 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 evalu-ated evaluated
              ated 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 spec-ifying specifying
              ifying  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 ALSO
       slapd.conf(5), slapd-config(5), slapd(8), slapadd(8), slapcat(8), slapindex(8), Berkeley DB  documen-tation. documentation.
       tation.

ACKNOWLEDGEMENTS
       OpenLDAP  Software  is  developed  and maintained by The OpenLDAP Project <http://www.openldap.org/>.
       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 2.4.28                                  2011/11/24                                     SLAPD-BDB(5)