Partial replication

Partial replication is a replication feature that replicates only the specified entries and a subset of attributes for the specified entries within a subtree. The entries and attributes that are to be replicated are specified by the LDAP administrator. Using partial replication, an administrator can enhance the replication bandwidth according to deployment requirements.

For instance, an administrator might choose the entries of the object class person with cn, sn, and userPassword attributes to be replicated and description attribute not to be replicated.

There are situations when administrator’s intervention is required for the smooth running of partial replication. These scenarios are listed.

Creating missing parent entries on the consumer

In filtered replication, an entry addition might fail displaying “No such object’ error because the parent entry does not exist on the consumer. It happens because the parent entry did not match the filter and was not replicated. In such cases, if the ibm-replicationCreateMissingEntries attribute is set to TRUE, the supplier must detect this error case and then generate and submit an add request for the missing entry before the supplier tries the add operation again instead of processing this case as an error. The missing entry must have the same DN as the immediate parent of the entry whose add failed. The missing entry belongs to the objectclass extensibleObject and contains operational attributes for create and modify timestamps as present on master server, that is, the timestamps are not modified when the entry is created on consumer. The missing entry must have ACLs as on the supplier server and must also have the description attribute value that is set to Missing entry created by master server.

Scenario

Sometimes the method to generate and submit a request to add a missing entry is recursive. The end condition is either a successful addition of all missing ancestors in the chain or a failure. The failure might occur during addition of any of the missing ancestors (for any reason other than NO_SUCH_OBJECT). If there is a failure, the change cannot be replicated and administrator intervention is required.

Workaround

The administrator must manually take care of handling errors when the ibm-replicationCreateMissingEntries attribute is set to FALSE. Administrators can also use error logs to identify the replication failure error messages that are logged in to error logs.

Modification in replication filter

Scenario

In partial replication, changes to replication filter can be dynamic. When a replication filter is changed, the data on the consumer would be in sync with the supplier cannot be assured.

Workaround

In cases where replication filter is changed, the administrator must take of such changes and reinitialize the consumer as per the new replication filter.

Note: The replication filter entry cannot be deleted if it is in use.