A catalog may contain one or more schemas. A schema is a persistent database object that provides a definition for part or all of the database. It represents a collection of database objects associated with a specific schema name. These objects include tables, views, indexes, stored procedures, triggers, and sequences. Schemas allow you to provide each user with his or her own database objects (such as tables) within the same logical database (that is, a single catalog). If no schema is specified with a database object, the default schema is the user id of the user creating the object.