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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:35:32 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:35:32 +0000 |
commit | 5ea77a75dd2d2158401331879f3c8f47940a732c (patch) | |
tree | d89dc06e9f4850a900f161e25f84e922c4f86cc8 /doc/man/man5/slapd-mdb.5 | |
parent | Initial commit. (diff) | |
download | openldap-5ea77a75dd2d2158401331879f3c8f47940a732c.tar.xz openldap-5ea77a75dd2d2158401331879f3c8f47940a732c.zip |
Adding upstream version 2.5.13+dfsg.upstream/2.5.13+dfsgupstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | doc/man/man5/slapd-mdb.5 | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/doc/man/man5/slapd-mdb.5 b/doc/man/man5/slapd-mdb.5 new file mode 100644 index 0000000..a6bb77c --- /dev/null +++ b/doc/man/man5/slapd-mdb.5 @@ -0,0 +1,241 @@ +.TH SLAPD-MDB 5 "RELEASEDATE" "OpenLDAP LDVERSION" +.\" Copyright 2011-2022 The OpenLDAP Foundation All Rights Reserved. +.\" Copying restrictions apply. See COPYRIGHT/LICENSE. +.\" $OpenLDAP$ +.SH NAME +slapd\-mdb \- Memory-Mapped DB backend to slapd +.SH SYNOPSIS +.B ETCDIR/slapd.conf +.SH DESCRIPTION +The \fBmdb\fP backend to +.BR slapd (8) +uses OpenLDAP's Lightning Memory-Mapped DB (LMDB) library to store data. +It relies completely on the underlying operating system for memory +management and does no caching of its own. It is the recommended +primary database backend. +.LP +The \fBmdb\fP backend uses a hierarchical database layout which +supports subtree renames. +.SH CONFIGURATION +These +.B slapd.conf +options apply to the \fBmdb\fP backend. +That is, they must follow a "backend mdb" line and +come before any subsequent "backend" or "database" lines. +.TP +.BI idlexp \ <exp> +Specify a power of 2 for the maximum size of an index slot. +The default is 16, yielding a maximum slot size of 2^16 or 65536. +Once set, this option applies to every \fBmdb\fP database instance. +The specified value must be in the range of 16-30. +.LP + +These +.B slapd.conf +options apply to the \fBmdb\fP 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 +.BR slapd.conf (5) +manual page. +.TP +.BI checkpoint \ <kbyte>\ <min> +Specify the frequency for flushing the database disk buffers. +This setting is only needed if the \fBdbnosync\fP option is used. +The checkpoint will occur if either \fI<kbyte>\fP data has been written or +\fI<min>\fP minutes have passed since the last checkpoint. +Both arguments default to zero, in which case they are ignored. When +the \fI<min>\fP argument is non-zero, an internal task will run every +\fI<min>\fP minutes to perform the checkpoint. +Note: currently the \fI<kbyte>\fP setting is unimplemented. +.TP +.B 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 transactions may be lost. +By default, a full data flush/sync is performed when each +transaction is committed. +.TP +.BI directory \ <directory> +Specify the directory where the LMDB files containing this database and +associated indexes live. +A separate directory must be specified for each database. +The default is +.BR LOCALSTATEDIR/openldap\-data . +.TP +\fBenvflags \fR{\fBnosync\fR,\fBnometasync\fR,\fBwritemap\fR,\fBmapasync\fR,\fBnordahead\fR} +Specify flags for finer-grained control of the LMDB library's operation. +.RS +.TP +.B nosync +This is exactly the same as the +.I dbnosync +directive. +.RE +.RS +.TP +.B nometasync +Flush the data on a commit, but skip the sync of the meta page. This mode is +slightly faster than doing a full sync, but can potentially lose the last +committed transaction if the operating system crashes. If both +.I nometasync +and +.I nosync +are set, the +.I nosync +flag takes precedence. +.RE +.RS +.TP +.B writemap +Use a writable memory map instead of just read-only. This speeds up write operations +but makes the database vulnerable to corruption in case any bugs in slapd +cause stray writes into the mmap region. +.RE +.RS +.TP +.B mapasync +When using a writable memory map and performing flushes on each commit, use an +asynchronous flush instead of a synchronous flush (the default). This option +has no effect if +.I writemap +has not been set. It also has no effect if +.I nosync +is set. +.RE +.RS +.TP +.B nordahead +Turn off file readahead. Usually the OS performs readahead on every read +request. This usually boosts read performance but can be harmful to +random access read performance if the system's memory is full and the DB +is larger than RAM. This option is not implemented on Windows. +.RE + +.TP +\fBindex \fR{\fI<attrlist>\fR|\fBdefault\fR} [\fBpres\fR,\fBeq\fR,\fBapprox\fR,\fBsub\fR,\fI<special>\fR] +Specify the indexes to maintain for the given attribute (or +list of attributes). +Some attributes only support a subset of indexes. +If only an \fI<attr>\fP is given, the indices specified for \fBdefault\fR +are maintained. +Note that setting a default does not imply that all attributes will be +indexed. Also, for best performance, an +.B eq +index should always be configured for the +.B objectClass +attribute. + +A number of special index parameters may be specified. +The index type +.B sub +can be decomposed into +.BR subinitial , +.BR subany ,\ and +.B subfinal +indices. +The special type +.B nolang +may be specified to disallow use of this index by language subtypes. +The special type +.B nosubtypes +may be specified to disallow use of this index by named subtypes. +Note: changing \fBindex\fP settings in +.BR slapd.conf (5) +requires rebuilding indices, see +.BR slapindex (8); +changing \fBindex\fP settings +dynamically by LDAPModifying "cn=config" automatically causes rebuilding +of the indices online in a background task. +.TP +.BI maxentrysize \ <bytes> +Specify the maximum size of an entry in bytes. Attempts to store +an entry larger than this size will be rejected with the error +LDAP_ADMINLIMIT_EXCEEDED. The default is 0, which is unlimited. +.TP +.BI 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. +.TP +.BI 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. +.TP +.BI mode \ <integer> +Specify the file protection mode that newly created database +files should have. +The default is 0600. +.TP +\fBmultival \fR{\fI<attrlist>\fR|\fBdefault\fR} \fI<integer hi>\fR,\fI<integer lo> +Specify the number of values for which a multivalued attribute is +stored in a separate table. Normally entries are stored as a single +blob inside the database. When an entry gets very large or contains +attributes with a very large number of values, modifications on that +entry may get very slow. Splitting the large attributes out to a separate +table can improve the performance of modification operations. +The threshold is specified as a pair of integers. If the number of +values exceeds the hi threshold the values will be split out. If +a modification deletes enough values to bring an attribute below +the lo threshold the values will be removed from the separate +table and merged back into the main entry blob. +The threshold can be set for a specific list of attributes, or +the default can be configured for all other attributes. +The default value for both hi and lo thresholds is UINT_MAX, which keeps +all attributes in the main blob. +.TP +.BI rtxnsize \ <entries> +Specify the maximum number of entries to process in a single read +transaction when executing a large search. Long-lived read transactions +prevent old database pages from being reused in write transactions, and +so can cause significant growth of the database file when there is +heavy write traffic. This setting causes the read transaction in +large searches to be released and reacquired after the given number +of entries has been read, to give writers the opportunity to +reclaim old database pages. The default is 10000. +.TP +.BI 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. +.SH ACCESS CONTROL +The +.B mdb +backend honors access control semantics as indicated in +.BR slapd.access (5). +.SH FILES +.TP +.B ETCDIR/slapd.conf +default +.B slapd +configuration file +.SH SEE ALSO +.BR slapd.conf (5), +.BR slapd\-config (5), +.BR slapd (8), +.BR slapadd (8), +.BR slapcat (8), +.BR slapindex (8), +.BR slapmodify (8), +OpenLDAP LMDB documentation. +.SH ACKNOWLEDGEMENTS +.so ../Project +Written by Howard Chu. |