H1: LDAP Sync Replication
-The LDAP Sync replication engine is designed to function as an
-improved alternative to {{slurpd}}(8). While the replication with
-{{slurpd}}(8) provides the replication capability for improved capacity,
-availability, and reliability, it has some drawbacks:
-
-^ It is {{not stateful}}, hence lacks the resynchronization capability.
-Because there is no representation of replica state in the replication
-with {{slurpd}}(8), it is not possible to provide an efficient
-mechanism to make the slave replica consistent to the master replica
-once they become out of sync. For instance, if the slave database
-content is damaged, the slave replica should be re-primed from the
-master replica again. with a state-based replication, it would be
-possible to recover the slave replica from a local backup. The slave
-replica, then, will be synchronized by calculating and transmitting
-the diffs between the slave replica and the master replica based
-on their states. The LDAP Sync replication is {{stateful}}.
-
-+ It is {{history-based}}, not {{state-based}}. The replication with
-{{slurpd}}(8) relies on the history information in the replication
-log file generated by {{slapd}}(8). If a portion of the log file
-that contains updates yet to be synchronized to the slave is truncated
-or damaged, a full reload is required. The state-based replication,
-on the other hand, would not rely on the separate history store.
-In the LDAP Sync replication, every directory entry has its state
-information in the {{EX:entryCSN}} operational attribute. The replica
-contents are calculated based on the consumer cookie and the
-{{EX:entryCSN}} of the directory entries.
-
-+ It is {{push-based}}, not {{pull-based}}. In the replication with
-{{slurpd}}(8), it is the master who decides when to synchronize the
-replica. The pull-based polling replication is not possible with
-{{slurpd}}(8). For example, in order to make a daily directory backup
-which is an exact image at a time, it is required to make the slave
-replica read-only by stopping {{slurpd}}(8) during backup. After backup,
-{{slurpd}}(8) can be run in an one-shot mode to resynchronize the slave
-replica with the updates during the backup. In a pull-based, polling
-replication, it is guaranteed to be read-only between the two polling
-points. The LDAP Sync replication supports both {{push-based}}
-and {{pull-based}} replication.
-
-+ It only supports the fractional replication and does not support
-the sparse replication. The LDAP Sync replication supports both the
-fractional and sparse replication. It is possible to use general
-search specification to initiate a synchronization session only for
-the interesting subset of the context.
-
-
-H2: LDAP Content Sync Protocol Description
-
-The LDAP Sync replication uses the LDAP Content Sync protocol (refer
-to the Internet Draft entitled "The LDAP Content Synchronization
-Operation") for replica synchronization. The LDAP Content Sync
-protocol operation is based on the replica state which is transmitted
-between replicas as the synchronization cookies. There are two
-operating modes: {{refreshOnly}} and {{refreshAndPersist}}. In both
-modes, a consumer {{slapd}}(8) connects to a provider {{slapd}}(8)
-with a cookie value representing the state of the consumer replica.
-The non-persistent part of the synchronization consists of two
-phases.
-
-The first is the {{state-based}} phase. The entries updated after
-the point in time the consumer cookie represents will be transmitted
-to the consumer. Because the unit of synchronization is entry, all
-the requested attributes will be transmitted even though only some
-of them are changed. For the rest of the entries, the present
-messages consisting only of the name and the synchronization control
-will be sent to the consumer. After the consumer receives all the
-updated and present entries, it can reliably make its replica
-consistent to the provider replica. The consumer will add all the
-newly added entries, replace the entries if updated entries are
-existent, and delete entries in the local replica if they are neither
-updated nor specified as present.
-
-The second is the {{log-based}} phase. This phase is incorporated
-to optimize the protocol with respect to the volume of the present
-traffic. If the provider maintains a history store from which the
-content to be synchronized can be reliably calculated, this log-base
-phase follows the state-base phase. In this mode, the actual directory
-update operations such as delete, modify, and add are transmitted.
-There is no need to send present messages in this log-based phase.
-
-If the protocol operates in the refreshOnly mode, the synchronization
-will terminate. The provider will send a synchronization cookie
-which reflects the new state to the consumer. The consumer will
-present the new cookie at the next time it requests a synchronization.
-If the protocol operates in the refreshAndPersist mode, the
-synchronization operation remains persistent in the provider. Every
-updates made to the provider replica will be transmitted to the
-consumer. Cookies can be sent to the consumer at any time by using
-the SyncInfo intermediate response and at the end of the synchronization
-by using the SyncDone control attached to the SearchResultDone
-message.
-
-Entries are uniquely identified by the {{EX:entryUUID}} attribute
-value in the LDAP Content Sync protocol. It can role as a reliable
-entry identifier while DN of an entry can change by modrdn operations.
-The {{EX:entryUUID}} is attached to each SearchResultEntry or
-SearchResultReference as a part of the Sync State control.
-
-
-H2: LDAP Sync Replication Details
-
-The LDAP Sync replication uses both the refreshOnly and the
-refreshAndPersist modes of synchronization. If an LDAP Sync replication
-is specified in a database definition, the {{slapd}}(8) schedules an
-execution of the LDAP Sync replication engine. In the refreshOnly
-mode, the engine will be rescheduled at the interval time after a
-replication session ends. In the refreshAndPersist mode, the engine
-will remain active to process the SearchResultEntry messages from
-the provider.
-
-The LDAP Sync replication uses only the state-base synchronization
-phase. Because {{slapd}}(8) does not currently implement history store
-like changelog or tombstone, it depends only on the state-base
-phase. A Null log-base phase follows the state-base phase.
-
-As an optimization, no entries will be transmitted to a consumer
-if there has been no update in the master replica after the last
-synchronization with the consumer. Even present messages for the
-unchanged entries are not transmitted. The consumer retains its
-replica contents.
-
-H3: entryCSN
-
-The LDAP Sync replication implemented in OpenLDAP stores state
-information to ever entry in the entryCSN attribute. entryCSN of
-an entry is the CSN or {{change sequence number}}, which is the
-refined timestamp, at which the entry was updated most lately. The
-CSN consists of three parts: the time, a replica ID, and a change
-count within a single second.
-
-H3: contextCSN
-
-contextCSN represents the current state of the provider replica.
-It is the largest entryCSN of all entries in the context such that
-no transaction having smaller entryCSN value remains outstanding.
-Because the entryCSN value is obtained before transaction start and
-transactions are not committed in the entryCSN order, special care
-needed to be taken to manage the proper contextCSN value in the
-transactional environment. Also, the state of the search result set
-is required to correspond to the contextCSN value returned to the
-consumer as a sync cookie.
-
-contextCSN, the provider replica state, is stored in the
-syncProviderSubentry. The value of the contextCSN is transmitted
-to the consumer replica as a Sync Cookie. The cookie is stored in
-the syncreplCookie attribute of syncConsumerSubentry subentry. The
-consumer will use the stored cookie value to represent its replica
-state when it connects to the provider in the future.
-
-H3: Glue Entry
-
-Because general search filter can be used in the LDAP Sync replication,
-an entry might be created without a parent, if the parent entry was
-filtered out. The LDAP Sync replication engine creates the glue
-entries for such holes in the replica. The glue entries will not
-be returned in response to a search to the consumer {{slapd}}(8) if
-manageDSAit is not set. It will be returned if it is set.
-
-H2: Configuring slapd for LDAP Sync Replication
-
-It is relatively simple to start servicing with a replicated OpenLDAP
-environment with the LDAP Sync replication, compared to the replication
-with {{slurpd}}(8). First, we should configure both the provider and
-the consumer {{slapd}}(8) servers appropriately. Then, start the provider
-slapd instance first, and the consumer slapd instance next.
-Administrative tasks such as database copy and temporal shutdown
-(or read-only demotion) of the provider are not required.
+The LDAP Sync replication engine, syncrepl for short, is a consumer-side
+replication engine that enables the consumer LDAP server to maintain
+a shadow copy of a DIT fragment. A syncrepl engine resides at the
+consumer-side as one of the {{slapd}} (8) threads. It creates and
+maintains a consumer replica by connecting to the replication provider
+to perform the initial DIT content load followed either by
+periodic content polling or by timely updates upon content changes.
+
+Syncrepl uses the LDAP Content Synchronization (or LDAP Sync for short)
+protocol as the replica synchronization protocol.
+
+Syncrepl provides a stateful replication which supports both the
+pull-based and the push-based synchronizations and does not mandate
+the use of the history store.
+
+Syncrepl keeps track of the status of the replication content by
+maintaining and exchanging synchronization cookies. Because the
+syncrepl consumer and provider maintain their content status,
+the consumer can poll the provider content to perform incremental
+synchronization by asking the entries required to make the consumer
+replica up-to-date with the provider content. Syncrepl also enables
+convenient management of replicas by maintaining replica status.
+The consumer replica can be constructed from a consumer-side or a
+provider-side backup at any synchronization status. Syncrepl can
+automatically resynchronize the consumer replica up-to-date with the
+current provider content.
+
+Syncrepl supports both the pull-based and the
+push-based synchronization. In its basic refreshOnly mode synchronization,
+the provider uses a pull-based synchronization where the consumer servers
+need not be tracked and no history information is maintained.
+The information required for the provider to process periodic polling
+requests is contained in the synchronization cookie of the request itself.
+To optimize the pull-based synchronization, syncrepl utilizes the present
+phase of the LDAP Sync protocol as well as its delete phase, instead of
+falling back on frequent full reloads. To further optimize the pull-based
+synchronization, the provider can maintain a per-scope session log
+as the history store. In its refreshAndPersist mode of synchronization,
+the provider uses a push-based synchronization. The provider keeps
+track of the consumer servers that have requested the persistent search
+and sends them necessary updates as the provider replication content
+gets modified.
+
+With syncrepl, a consumer server can create a replica without changing
+provider's configurations and without restarting the provider server,
+if the consumer server has appropriate access privileges for the
+DIT fragment to be replicated. The consumer server can stop the
+replication also without the need for provider-side changes and restart.
+
+Syncrepl supports both partial and sparse replications.
+The shadow DIT fragment is defined by a general
+search criteria consisting of base, scope, filter, and attribute list.
+The replica content is also subject to the access privileges
+of the bind identity of the syncrepl replication connection.
+
+
+H2: The LDAP Content Synchronization Protocol
+
+The LDAP Sync protocol allows a client to maintain a synchronized copy
+of a DIT fragment. The LDAP Sync operation is defined as a set of
+controls and other protocol elements which extend the LDAP search
+operation. This section introduces the LDAP Content Sync protocol
+only briefly. For more information, refer to the Internet Draft
+{{The LDAP Content Synchronization Operation
+<draft-zeilenga-ldup-sync-05.txt>}}.
+
+The LDAP Sync protocol supports both polling and listening for
+changes by defining two respective synchronization operations:
+{{refreshOnly}} and {{refreshAndPersist}}.
+The polling is implemented by the {{refreshOnly}} operation.
+The client copy is synchronized to the server copy at the time of polling.
+The server finishes the search operation by returning {{SearchResultDone}}
+at the end of the search operation as in the normal search.
+The listening is implemented by the {{refreshAndPersist}} operation.
+Instead of finishing the search after returning all entries currently
+matching the search criteria, the synchronization search remains
+persistent in the server. Subsequent updates to the synchronization content
+in the server have additional entry updates be sent to the client.
+
+The {{refreshOnly}} operation and the refresh stage of the
+{{refreshAndPersist}} operation can be performed by
+a present phase or a delete phase.
+
+In the present phase, the server sends the client the entries updated
+within the search scope since the last synchronization. The server sends
+all requested attributes, be it changed or not, of the updated entries.
+For each unchanged entry which remains in the scope,
+the server sends a present message consisting only of the name of the
+entry and the synchronization control representing state present.
+The present message does not contain any attributes of the entry.
+After the client receives all update and present entries,
+it can reliably determine the new client copy by adding the entries
+added to the server, by replacing the entries modified at the server,
+and by deleting entries in the client copy which have not
+been updated nor specified as being present at the server.
+
+The transmission of the updated entries in the delete phase is
+the same as in the present phase. The server sends all the requested
+attributes of the entries updated within the search scope since the
+last synchronization to the client. In the delete phase, however,
+the server sends a delete message for each entry deleted from the
+search scope, instead of sending present messages.
+The delete message consists only of the name of the entry
+and the synchronization control representing state delete.
+The new client copy can be determined by adding, modifying, and
+removing entries according to the synchronization control
+attached to the {{SearchResultEntry}} message.
+
+In the case that the LDAP Sync server maintains a history store
+and can determine which entries are scoped out of the client
+copy since the last synchronization time, the server can use
+the delete phase. If the server does not maintain any history store,
+cannot determine the scoped-out entries from the history store,
+or the history store does not cover the outdated synchronization
+state of the client, the server should use the present phase.
+The use of the present phase is much more efficient than a full
+content reload in terms of the synchronization traffic.
+To reduce the synchronization traffic further,
+the LDAP Sync protocol also provides several optimizations
+such as the transmission of the normalized {{EX:entryUUID}}s and the
+transmission of the multiple {{EX:entryUUIDs}} in a single
+{{syncIdSet}} message.
+
+At the end of the {{refreshOnly}} synchronization,
+the server sends a synchronization cookie to the client as a state
+indicator of the client copy after the synchronization is completed.
+The client will present the received cookie when it requests
+the next incremental synchronization to the server.
+
+When {{refreshAndPersist}} synchronization is used,
+the server sends a synchronization cookie at the end of the
+refresh stage by sending a Sync Info message with TRUE refreshDone.
+It also sends a synchronization cookie by attaching it to
+{{SearchResultEntry}} generated in the persist stage of the
+synchronization search. During the persist stage, the server
+can also send a Sync Info message containing the synchronization
+cookie at any time the server wants to update the client-side state
+indicator. The server also updates a synchronization indicator
+of the client at the end of the persist stage.
+
+In the LDAP Sync protocol, entries are uniquely identified by
+the {{EX:entryUUID}} attribute value. It can function as a reliable
+identifier of the entry. The DN of the entry, on the other hand,
+can be changed over time and hence cannot be considered as the reliable
+identifier. The {{EX:entryUUID}} is attached to each {{SearchResultEntry}}
+or {{SearchResultReference}} as a part of the synchronization control.
+
+
+H2: Syncrepl Details
+
+The syncrepl engine utilizes both the {{refreshOnly}} and the
+{{refreshAndPersist}} operations of the LDAP Sync protocol.
+If a syncrepl specification is included in a database definition,
+{{slapd}} (8) launches a syncrepl engine as a {{slapd}} (8) thread
+and schedules its execution. If the {{refreshOnly}} operation is
+specified, the syncrepl engine will be rescheduled at the interval
+time after a synchronization operation is completed.
+If the {{refreshAndPersist}} operation is specified, the engine will
+remain active and process the persistent synchronization messages
+from the provider.
+
+The syncrepl engine utilizes both the present phase and the
+delete phase of the refresh synchronization. It is possible to
+configure a per-scope session log in the provider server
+which stores the {{EX:entryUUID}}s and the names of a finite
+number of entries deleted from a replication content.
+Multiple replicas of single provider content share the same
+per-scope session log. The syncrepl engine uses the delete phase
+if the session log is present and the state of the consumer
+server is recent enough that no session log entries are truncated
+after the last synchronization of the client.
+The syncrepl engine uses the present phase if no session log
+is configured for the replication content or if the
+consumer replica is too outdated to be covered by the session log.
+The current design of the session log store is memory based, so
+the information contained in the session log is not persistent
+over multiple provider invocations. It is not currently supported
+to access the session log store by using LDAP operations. It is
+also not currently supported to impose access control to the session log.
+
+As a further optimization, even in the case the synchronization search
+is not associated with any session log, no entries will be transmitted
+to the consumer server when there has been no update in the replication
+context.
+
+While {{slapd}} (8) can function as the LDAP Sync provider only
+when it is configured with either {{back-bdb}} or {{back-hdb}} backend,
+the syncrepl engine, which is a consumer-side replication engine,
+can work with any backends.
+
+The LDAP Sync provider maintains {{EX:contextCSN}} for each
+database as the current synchronization state indicator of the
+provider content. It is the largest {{EX:entryCSN}} in the provider
+context such that no transactions for an entry having
+smaller {{EX:entryCSN}} value remains outstanding.
+{{EX:contextCSN}} could not just be set to the largest issued
+{{EX:entryCSN}} because {{EX:entryCSN}} is obtained before
+a transaction starts and transactions are not committed in the
+issue order.
+
+The provider stores the {{EX:contextCSN}} of a context in the
+{{EX:syncreplCookie}} attribute of the immediate child entry of
+the context suffix whose DN is {{cn=ldapsync,<suffix>}} and
+object class is {{EX:syncProviderSubentry}}.
+
+The consumer stores its replica state, which is the provider's
+{{EX:contextCSN}} received as a synchronization cookie,
+in the {{EX:syncreplCookie}} attribute of the immediate child
+of the context suffix whose DN is {{cn=syncrepl<rid>,<suffix>}}
+and object class is {{EX:syncConsumerSubentry}}.
+The replica state maintained by a consumer server is used as the
+synchronization state indicator when it performs subsequent incremental
+synchronization with the provider server. It is also used as a
+provider-side synchronization state indicator when it functions as
+a secondary provider server in a cascading replication configuration.
+<rid> is the replica ID uniquely identifying the replica locally in the
+syncrepl consumer server. <rid> is an integer which has no more than
+three decimal digits.
+
+Because a general search filter can be used in the syncrepl specification,
+not all entries in the context will be returned as the synchronization content.
+The syncrepl engine creates a glue entry to fill in the holes
+in the replica context if any part of the replica content is
+subordinate to the holes. The glue entries will not be returned
+as the search result unless {{ManageDsaIT}} control is provided.
+
+It is possible to retrieve {{EX:syncProviderSubentry}} and
+{{EX:syncConsumerSubentry}} by performing an LDAP search with
+the respective entries as the base object and with the base scope.
+
+
+H2: Configuring Syncrepl
+
+Because syncrepl is a consumer-side replication engine, the syncrepl
+specification is defined in {{slapd.conf}} (5) of the consumer server,
+not in the provider server's configuration file.
+The initial loading of the replica content can be performed either
+by starting the syncrepl engine with no synchronization cookie
+or by populating the consumer replica by adding and demoting an
+{{TERM:LDIF}} file dumped as a backup at the provider.
+{{slapadd}} (8) supports the replica promotion and demotion.
+
+When loading from a backup, it is not required to perform the initial
+loading from the up-to-date backup of the provider content. The syncrepl
+engine will automatically synchronize the initial consumer replica to
+the current provider content. As a result, it is not required
+to stop the provider server in order to avoid the replica inconsistency
+caused by the updates to the provider content during the
+content backup and loading process.
+
+When replicating a large scale directory, especially in a bandwidth
+constrained environment, it is advised to load the consumer replica
+from a backup instead of performing a full initial load using syncrepl.
H3: Set up the provider slapd
-There is no special slapd.conf(5) directive for the provider {{slapd}}(8).
-Because the LDAP Sync searches are subject to access control, proper
-access control privileges should be set up for the replicated
-content.
-
-When creating a provider database from an ldif file using {{slapadd}}(8),
-you must create and update a state indicator of the database context
-up to date. slapadd(8) will store the contextCSN in the
-syncProviderSubentry if it is given the {{EX:-w}} flag. It is also
-possible to create the syncProviderSubentry with an appropriate
-contextCSN value by directly including it in the ldif file. If
-{{slapadd}}(8) runs without the {{EX:-w}} flag, the provided
-contextCSN will be stored. With the {{EX:-w}} flag, a new value
-based on the current time will be stored as contextCSN. {{slapcat}}(8)
-can be used to retrieve the directory with the contextCSN when it
-is run with the {{EX:-m}} flag.
-
-Only the BDB (back-bdb) and HDB (back-hdb) backends can perform as
-the LDAP Sync replication provider. Back-ldbm currently does not
-have the LDAP Content Sync protocol functionality.
+There is no special {{slapd.conf}} (5) directive for the provider
+syncrepl server except for the session log directive. Because the
+LDAP Sync search is subject to access control, proper access control
+privileges should be set up for the replicated content.
+
+When creating a provider database from the {{TERM:LDIF}} file using
+{{slapadd}} (8), {{EX:contextCSN}} and the {{EX:syncProviderSubentry}}
+entry must be created. {{slapadd -p -w}} will create
+a new {{EX:contextCSN}} from the {{EX:entryCSN}}s of the added entries.
+It is also possible to create the {{EX:syncProviderSubentry}} with
+an appropriate {{EX:contextCSN}} value by directly including it
+in the ldif file. {{slapadd -p}} will preserve the provider's
+contextCSN or will change it to the consumer's contextCSN
+if it is to promote a replica to the provider's content.
+The {{EX:syncProviderSubentry}} can be included in the ldif output
+when {{slapcat}} (8) is given the {{-m}} flag;
+the {{EX:syncConsumerSubentry}} can be retrieved by the {{-k}}
+flag of {{slapcat}} (8).
+
+The session log is configured by
+
+> sessionlog <sid> <limit>
+
+directive, where {{<sid>}} is the ID of the per-scope session log
+in the provider server and {{<limit>}} is the maximum number of
+session log entries the session log store can record. {{<sid>}}
+is an integer no longer than 3 decimal digits. If the consumer
+server sends a synchronization cookie containing {{sid=<sid>}}
+where {{<sid>}} matches the session log ID specified in the directive,
+the LDAP Sync search is to utilize the session log store.
H3: Set up the consumer slapd
-The consumer slapd is configured by {{slapd.conf}}(5) configuration
-file. For the configuration directives, see the {{SECT:syncrepl}}
-section of {{SECT:The slapd Configuration File}} chapter. In the
-configuration file, make sure the DN given in the {{EX:updatedn=}}
-directive of the syncrepl specification has permission to write to
-the database. Below is an example syncrepl specification at the
-consumer replica :
+The syncrepl replication is specified in the database section
+of {{slapd.conf}} (5) for the replica context.
+The syncrepl engine is backend independent and the directive
+can be defined with any database type.
-> syncrepl id = 1
+> syncrepl rid=123
> provider=ldap://provider.example.com:389
-> updatedn="cn=replica,dc=example,dc=com"
-> binddn="cn=syncuser,dc=example,dc=com"
-> bindmethod=simple
-> credentials=secret
+> type=refreshOnly
+> interval=01:00:00:00
> searchbase="dc=example,dc=com"
> filter="(objectClass=organizationalPerson)"
-> attrs="cn,sn,ou,telephoneNumber,title,l"
-> schemachecking=on
> scope=sub
-> type=refreshOnly
-> interval=01:00:00
+> attrs="cn,sn,ou,telephoneNumber,title,l"
+> schemachecking=off
+> updatedn="cn=replica,dc=example,dc=com"
+> bindmethod=simple
+> binddn="cn=syncuser,dc=example,dc=com"
+> credentials=secret
In this example, the consumer will connect to the provider slapd
at port 389 of {{FILE:ldap://provider.example.com}} to perform a
-polling (refreshOnly) mode of synchronization once a day. It will
+polling ({{refreshOnly}}) mode of synchronization once a day. It will
bind as {{EX:cn=syncuser,dc=example,dc=com}} using simple authentication
with password "secret". Note that the access control privilege of
-the DN specified by the binddn= directive should be set properly
-to synchronize the desired replica content. The consumer will write
-to its database with the privilege of the
-{EX:cn=replica,dc=example,dc=com}} entry as specified by the
-{{EX:updatedn=}} directive. The updatedn entry should have write
-permission to the database.
-
-The synchronization search in the example will search for entries
-whose objectClass is organizationalPerson in the entire subtree
-under {{EX:dc=example,dc=com}} search base inclusively. The requested
-attributes are cn, sn, ou, telephoneNumber, title, and l. The schema
-checking is turned on, so that the consumer {{slapd}}(8) will enforce
-entry schema checking when it process updates from the provider
-{{slapd}}(8).
-
-The LDAP Sync replication engine is backend independent. All three
-native backends can perform as the LDAP Sync replication consumer.
+{{EX:cn=syncuser,dc=example,dc=com}} should be set appropriately
+in the provider to retrieve the desired replication content.
+The consumer will write to its database with the privilege of the
+{{EX:cn=replica,dc=example,dc=com}} entry as specified in the
+{{EX:updatedn=}} directive. The {{EX:updatedn}} entry should have
+write permission to the replica content.
+
+The synchronization search in the above example will search for the
+entries whose objectClass is organizationalPerson in the entire subtree
+rooted at {{EX:dc=example,dc=com}}. The requested attributes are
+{{EX:cn}}, {{EX:sn}}, {{EX:ou}}, {{EX:telephoneNumber}},
+{{EX:title}}, and {{EX:l}}. The schema checking is turned off, so
+that the consumer {{slapd}} (8) will not enforce entry schema checking
+when it process updates from the provider {{slapd}} (8).
+
+For more detailed information on the syncrepl directive,
+see the {{SECT:syncrepl}} section of {{SECT:The slapd Configuration File}}
+chapter of this admin guide.
H3: Start the provider and the consumer slapd
-If the currently running provider {{slapd}}(8) already has the
-syncProviderSubentry in its database, it is not required to restart
-the provider slapd. You don't need to restart the provider {{slapd}}(8)
-when you start a replicated LDAP service. When you run a consumer
-{{slapd}}(8), it will immediately perform either the initial full reload
-if cookie is NULL or too out of date, or incremental synchronization
-if effective cookie is provided. In the refreshOnly mode, the next
-synchronization session is scheduled to run interval time after the
-completion of the current session. In the refreshAndPersist mode,
-the synchronization session is open between the consumer and provider.
-The provider will send update message whenever there are updates
-in the provider replica.
+The provider {{slapd}} (8) is not required to be restarted.
+{{contextCSN}} is automatically generated as needed:
+it might originally contained in the {{TERM:LDIF}} file,
+generated by {{slapadd}} (8), generated upon changes in the context,
+or generated when the first LDAP Sync search arrived at the provider.
+
+When starting a consumer {{slapd}} (8), it is possible to provide a
+synchronization cookie as the {{-c cookie}} command line option
+in order to start the synchronization from a specific state.
+The cookie is a comma separated list of name=value pairs. Currently
+supported syncrepl cookie fields are {{csn=<csn>}}, {{sid=<sid>}}, and
+{{rid=<rid>}}. {{<csn>}} represents the current synchronization state
+of the consumer replica. {{<sid>}} is the identity of the per-scope
+session log to which this consumer will be associated. {{<rid>}} identifies
+a consumer replica locally within the consumer server. It is used to relate
+the cookie to the syncrepl definition in {{slapd.conf}} (5) which has
+the matching replica identifier.
+Both {{<sid>}} and {{<rid>}} have no more than 3 decimal digits.
+The command line cookie overrides the synchronization cookie
+stored in the consumer replica database.
projects / openldap / blobdiff