Fractional Replication

By default, the replication operation copies entire entries in the replicated suffix to consumer replicas. With the fractional replication feature, you can select the suffix that you want to use, and which attributes you want to include or exclude. Fractional replication is configured in the replication agreement, allowing you to define the attribute set for each consumer replicated suffix of a master. You can control which data is distributed and use replication bandwidth and consumer resources more efficiently.

For example, if you want to reduce replication bandwidth, you can choose not to replicate attributes with typically large values such as photo, jpegPhoto, and audio. As a result, these attributes will not be available on consumers. As another example, you can choose to replicate only the uid and userpassword attributes to a consumer server that is dedicated to performing authentication.

Considerations for Fractional Replication

Fractional replication cannot be used in versions of the product prior to Directory Server 5.2. When configuring a fractional replication agreement, both the master and consumer replicas must use at least Directory Server 5.2.

Enabling or modifying a fractional set of attributes requires you to reinitialize the consumer replica. Therefore, you need to determine your fractional replication needs before deployment and define your attribute set before you initialize your replicated suffixes for the first time.

You need to proceed with caution when replicating a small set of attributes, given the dependency of complex features such as ACIs, roles, and CoS on certain attributes. In addition, not replicating other attributes that are mentioned in specifiers or filters of the ACI, roles, or CoS mechanisms might compromise the security of the data. Not replicating might also result in different sets of attributes being returned in searches. Managing a list of attributes to exclude is safer, and less prone to human error, than managing a list of attributes to include.

You need to turn off schema checking in the consumer server if the attribute set that you replicate does not allow all replicated entries to follow the schema. Replication of non-conforming entries does not cause errors because the replication mechanism bypasses schema checking on the consumer. However, the consumer will contain non-conforming entries and should have schema checking turned off to expose a coherent state to its clients.

Fractional replication is configured in the replication agreement of master replicas with hubs and dedicated consumers. Configuration of fractional replication between two master replicas in a multimaster replication environment is not supported. Also, if several masters have replication agreements with the same replica, all these agreements must replicate the same set of attributes.

To Configure Fractional Replication

To configure fractional replication, you must specify the suffix, determine whether to include or exclude attributes on that suffix, then choose which attributes to include or exclude. If you choose to exclude attributes on a suffix, all other attributes are automatically included. Likewise, if you choose to include certain attributes on a suffix, all other attributes are automatically excluded.

You can use DSCC to perform this task. For information, see Directory Service Control Center Interface and the DSCC online help.

Configure fractional replication on a replication agreement located on the source server.

$ dsconf set-repl-agmt-prop -h host -p port suffix-DN consumer-host:consumer-port property:value

where property is either repl-fractional-exclude-attr or repl-fractional-include-attr.

For example, if you want to configure a fractional agreement to exclude JPEG and TIFF photos from being replicated on the suffix dc=example,dc=com, use this command:

$ dsconf set-repl-agmt-prop -h host2 -p 1389 dc=example,dc=com host1:1389 repl-fractional-exclude-attr:jpegPhoto repl-fractional-exclude-attr:tiffPhoto