Fractional Replication

The fractional replication feature enables you to restrict certain attributes from being included when modify operations are replayed on specific servers in a topology. For information about configuring fractional replication, see Configuring Fractional Replication in Oracle Fusion Middleware Administration Guide for Oracle Unified Directory.

This section describes the architecture of the fractional replication mechanism and covers the following topics:

• Fractional Data Set Identification

• Fractional Replication Filtering

• Fractional Replication and Local Operations

Fractional Data Set Identification

A fractional data set is identified by the following operational attributes that are stored in the root entry of the replicated domain:

• ds-sync-fractional-exclude

• ds-sync-fractional-include

The syntax and meaning of these attributes is identical to their corresponding configuration attributes, described in Configuring Fractional Replication in Oracle Fusion Middleware Administration Guide for Oracle Unified Directory. The role of these operational attributes is to tag a data set as fractional: their presence in a domain implies “this data set is a fractional domain and does not contain the following specific attributes...”.

The fractional configuration stored in the root entry of the domain, combined with the generation ID (ds-sync-generation-id) and the replication state (ds-sync-state), can be seen as the fractional signature of the data set.

When a domain is enabled (for example, after its fractional configuration is modified), the server compares the fractional configuration of the domain (under cn=config) with the fractional configuration attributes in the root entry of the domain. If both configurations match, the domain assumes a normal status and LDAP operations can be accepted. If the configurations do not match, the domain assumes a bad generation ID status and the data set must be synchronized (by importing a data set) before LDAP operations can be accepted.

The data set that is imported must either:

• have the same fractional configuration in its root entry as the local domain has under cn=config. In this case, the data set is imported as is.

• have no fractional configuration in its root entry. In this case, the data set is imported and filtered according to the attribute filtering rules defined in the fractional configuration of the local domain (under cn=config). The ds-sync-fractional-exclude or ds-sync-fractional-include attributes are then created in the root entry of the imported data, by copying the fractional configuration of the local domain.

Fractional Replication Filtering

When a domain is configured as fractional, all ADD, MODIFY, and MODIFYDN operations that arrive from the network to be replayed are filtered. These operations can end up being abandoned if all of the attributes in the operation are filtered attributes according to the fractional configuration.

Fractional Replication and Local Operations

If an LDAP client performs an operation directly on a fractional replica and the operation does not match the fractional configuration, the operation is forbidden and the server returns an “unwilling to perform” error.

For example, if a fractional replica is configured with fractional-exclude: *:jpegPhoto and an LDAP client attempts to add a new entry that contains a jpegPhoto attribute, the operation is rejected with an “unwilling to perform” error. This behavior ensures that the domain remains consistent with its fractional configuration definition, which implies that no jpegPhoto attribute can exist on the domain.