If you want tables to be created from scratch each time you run the conversion, leave this at Recreate tables. If table already exists in target, it will first be dropped, then created.
To load the existing tables in target with data, but not touch the structure (used when you want to preserve existing structure and relationships), select Expect existing.
If you want tables to contain same data as source tables, leave this at Recreate data. We will delete data existing in target table, then copy all data from source table over.
In some cases, it may make sense to append data on each run. Use Append data if you have tables containing only data to be appended each time you run the conversion - typically that's the case if you receive daily data using CSV or DBF export from another database. Please note that this option does not do a copying of changes only - for that (called replication) you will need our Omega Sync or Replicator product.