Two programs are available for combining database files. APPEND lets you add new records to one database from another database. JOIN lets you merge databases that have different parameter sets, but have the same key values, e.g., the same shot numbers. EXTRACT lets you create a new database from a subset of an existing database. This is useful if you have a large database and want to look at the same subset repeatedly. RECLAIM reclaims disk space that is lost when records are deleted. This should be used if you've deleted lots of records from your database.