Oracle Security

Types of Database Files

The database is comprised of several different types of files that serve different functions within the system. We describe each component in the following sections.

Tablespace and Tablespace Datafiles

A tablespace is an internal object used to represent a physical storage area. It is the logical name for an entity used to access the operating system files called datafiles. In this book, when we speak of a tablespace we will mean the logical tablespace name as well as the files assigned to it. Oracle uses a tablespace to house the following different kinds of structures:

• Database object structures—like tables, indexes, packages, procedures, triggers, etc.

• Rollback segments

• Temporary sort segments

A tablespace must have one or more datafiles assigned to it; otherwise, it cannot be created. These files may be on one or more disks. When you create a table or index, you will specify the tablespace in which the object is to be created. If this is not done, then your default tablespace will be used. The STORAGE clause used in the CREATE statement will determine how much space is allocated from the tablespace. Several examples of STORAGE clauses appear in the following sections. When this initial allocation is filled, more space will be assigned, this time according to the NEXT parameter in the STORAGE clause. The DBA monitors space utilization and, as the tablespace becomes full, will need to add more datafiles or rebuild the tablespace to combine the current datafiles ...