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SLAPD-MDB(5)                                                                                    SLAPD-MDB(5)



NAME
       slapd-mdb - Memory-Mapped DB backend to slapd

SYNOPSIS
       /etc/openldap/slapd.conf

DESCRIPTION
       The  mdb  backend  to  slapd(8) uses OpenLDAP's own Memory-Mapped DB (MDB) library to store data.  It
       relies completely on the underlying operating system for memory management and does no caching of its
       own.

       The  mdb  backend  is similar to the hdb backend in that it uses a hierarchical database layout which
       supports subtree renames. It is both more space-efficient and more execution-efficient than  the  bdb
       backend, while being overall much simpler to manage.

CONFIGURATION
       These  slapd.conf  options  apply to the mdb backend database.  That is, they must follow a "database
       mdb" line and come before any subsequent "backend" or "database" lines.  Other database  options  are
       described in the slapd.conf(5) manual page.

       checkpoint <kbyte> <min>
              Specify  the frequency for flushing the database disk buffers.  This setting is only needed if
              the dbnosync option is used.  The checkpoint will occur if either <kbyte> data has been  writ-ten written
              ten  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.  Note: currently the <kbyte> setting is unim-plemented. unimplemented.
              plemented.

       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. In
              particular, if the operating system crashes before changes are flushed, some number of  trans-actions transactions
              actions may be lost.  By default, a full data flush/sync is performed when each transaction is
              committed.

       directory <directory>
              Specify the directory where the MDB 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.

       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.

       maxreaders <integer>
              Specify the maximum number of threads that may have concurrent read access  to  the  database.
              Tools  such  as  slapcat  count as a single thread, in addition to threads in any active slapd
              processes. The default is 126.

       maxsize <bytes>
              Specify the maximum size of the database in bytes. A memory map of this size is  allocated  at
              startup  time  and  the  database will not be allowed to grow beyond this size. The default is
              10485760 bytes. This setting may be changed  upward  if  the  configured  limit  needs  to  be
              increased.

              Note:  It  is  important to set this to as large a value as possible, (relative to anticipated
              growth of the actual data over time) since growing the size later may not  be  practical  when
              the system is under heavy load.

       mode <integer>
              Specify  the  file protection mode that newly created database 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.

ACCESS CONTROL
       The mdb backend honors access control semantics as indicated in slapd.access(5).

NOTES
       This  is  an early release; the database file format or other characteristics may change incompatibly
       in future releases.

FILES
       /etc/openldap/slapd.conf
              default slapd configuration file

SEE ALSO
       slapd.conf(5), slapd-config(5), slapd(8), slapadd(8), slapcat(8), slapindex(8), OpenLDAP MDB 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.  Written by Howard Chu.



OpenLDAP 2.4.28                                  2011/11/24                                     SLAPD-MDB(5)