The optdiag utility command allows you to load simulated statistics and perform query diagnosis using those statistics. Since you can load simulated statistics even for tables that are empty, using simulated statistics allows you to perform tuning diagnostics in a very small database that contains only the tables and indexes. Simulated statistics do not overwrite any existing statistics when they are loaded, so you can also load them into an existing database.
Once simulated statistics have been loaded, instruct the optimizer to use them (rather than the actual statistics):
set statistics simulate on
For complete information on using simulated statistics, see “Using simulated statistics”.