Packages deployed to Unwired Server are identified with a unique version.
Multiple versions of the same package can be running simultaneously, which means the consolidated database (or cache) includes multiple copies of the same data until all mobile applications have been switched to a new version. As a caution, there is always a consistency issue between multiple copies of the data.
Message-based synchronization uses subscription information to determine if there are any outstanding mobile applications that still subscribe to a particular version of the package.
Replication-based synchronization has no such information to reliably determine if there are still referencing mobile applications. Sybase suggests that you set up best practices for modifying and deploying new versions of mobile business objects and packages.