Commit writes the XML but does not alter the metabase. The existing XML model and metabase are kept, and a new version of the XML is written out so that two versions of the XML model are stored.
If you do an incremental commit on a model multiple times before you perform a Model Update, the kernel combines the individual lists of tables in the commit’s delta files into one list of tables. See the Getting Started Guide for information on committing a model and delta files.