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slapo-syncprov - Sync Provider overlay to slapd




The Sync Provider overlay implements the provider-side support for the LDAP Content Synchronization (RFC4533) as well as syncrepl replication support. The overlay can be used with any backend that maintains entryCSN and entryUUID attributes for its entries. It also creates a contextCSN attribute in the root entry of the database.

The contextCSN is updated for every write operation performed against the database. To reduce database contention, the contextCSN is only updated in memory. The value is written to the database on server shutdown and read into memory on startup, and maintained in memory thereafter. Checkpoints may be configured to write the contextCSN into the underlying database to minimize recovery time after an unclean shutdown.

On databases that support inequality indexing, it is highly recommended to set an eq index on the entryCSN attribute when using this overlay.


These slapd.conf options apply to the Sync Provider overlay. They should appear after the overlay directive.

After a write operation has succeeded, write the contextCSN to the underlying database if <ops> write operations or more than <minutes> time have passed since the last checkpoint. Checkpointing is disabled by default.
Configures an in-memory session log for recording information about write operations made on the database. The <ops> specifies the number of operations that are recorded in the log. All write operations (except Adds) are recorded in the log. When using the session log, it is helpful to set an eq index on the entryUUID attribute in the underlying database.
Should not be set when syncprov-sessionlog is set and vice versa.

When accesslog for this database is configured and is logging at this suffix, it can be used as the session log source instead of the in-memory session log mentioned above. This log has the advantage of not starting afresh every time the server is restarted.

Specify that the Present phase of refreshing should be skipped. This value should only be set TRUE for a syncprov instance on top of a log database (such as one managed by the accesslog overlay). The default is FALSE.
Specify that the overlay should honor the reloadHint flag in the Sync Control. It must be set TRUE when using the accesslog overlay for delta-based syncrepl replication support. The default is FALSE.


default slapd configuration file


slapd.conf(5), slapd-config(5), slapo-accesslog(5). OpenLDAP Administrator's Guide.


OpenLDAP Software is developed and maintained by The OpenLDAP Project <>. OpenLDAP Software is derived from the University of Michigan LDAP 3.3 Release.

2022/07/14 OpenLDAP 2.5.13+dfsg-5