Directory Server provides a mechanism for adding new entries to an existing database. This import process checks if a given entry already exists so that data is not overwritten. This feature allows you to import an LDIF file in multiple passes at different times. Successive imports do not delete what already exists in the database.
For more information about importing entries to large replicated suffixes, see Incrementally Adding Many Entries to Large Replicated Suffixes in Sun Java System Directory Server Enterprise Edition 6.1 Administration Guide.