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Common Objects


Notes:

As an application developer, you will need to know about several objects that can be created. These include:
Schema – A schema is a logical group of objects all owned by the same user. So, when user DAVE is first created, the schema is empty. If DAVE executes a CREATE TABLE command, the schema has one object.
Table – A table is the basic unit of storage in Oracle. Most tables are simple structures of columns and rows. However, with the advent of object support, a table can contain objects (complex user-defined datatypes that model real-world objects) or even be an object table (contains objects rather than columns and rows). A table is identified by a schema name and a table name, for example DAVE.CUSTOMER.
Tablespace – A tablespace is a logical repository of other objects such as tables and indexes. A tablespace points to one or more datafiles – actual disk files that contain the blocks that make up our database. We often group related tables and indexes in the same tablespace for administrative reasons. For example, you can take an entire tablespace offline with one simple command.
Index – An index is an object that contains pointers to table data and is created to improve the performance of access to a table. Once created, an index is automatically and transparently maintained by Oracle as inserts, updates and deletes occur against the related table.