The database manager maintains a set of tables containing information about the data in the database. These tables are collectively known as the catalog. The catalog tables contain information about tables, parameters, procedures, packages, views, indexes, and constraints on the AS/400 system.
The database manager provides views over the catalog tables. The views provide more consistency with the catalog views of other IBM SQL products and with the catalog views of the ANSI and ISO standard (called Information Schema in the standard). The catalog views in QSYS2 contain information about all tables, packages, views, indexes, and constraints on the AS/400 system. Additionally, an SQL collection will contain a set of these views that only contains information about tables, packages, views, indexes, and constraints in the collection.
Tables and views in the catalog are like any other database tables and views. If you have authorization, you can use SQL statements to look at data in the catalog views in the same way that you retrieve data from any other table in the AS/400 system. The database manager ensures that the catalog contains accurate descriptions of the objects in the database at all times.
For more information about catalog tables and views, see Appendix G, "DB2 UDB for AS/400 Catalog Views".