Rolling back databases to R4 database format
Once you upgrade an application or database to Release 5 format (ODS), you can roll back to an earlier ODS version by using Compact -R, compacting from the Domino Administrator, or by creating a new replica or copy of the database in R4 format. Notes clients from Release 4 can access Release 5 databases on Release 5 servers, but you cannot use a Release 5 database on a Domino server running an earlier version of the software.
The Release 5 database format does not replicate, and Release 4 servers ignore unsupported Release 5 features, so you can safely replicate a database replica that has been upgraded to Release 5 database format with a replica that has not.