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Tablespace is a fancy Oracle Database 10g name for a database file. Think of it as a space where a table resides. As an Oracle Database 10g is created, a system tablespace is built that contains Oracle's data dictionary. As Oracle Database 10g operates, it continually gets operational information out of its data dictionary and, as records are created, this system tablespace defines attributes of the data it stores, such as:
The data type of pieces of information. Are they numeric, alphanumeric, or perhaps binary of some video or audio format?
The maximum allowable size of fields as they are populated by the applications. This is where, for example, a country description is defined as from one to 30 characters long, and containing only letters.
Who owns the information as the database data files are populated?
Who is allowed to look at each other's data and what types of activities each user of the database can perform on that data?
The system tablespace is a very close cousin of the sysaux tablespace discussed next.
Many of the tools and options that support the Oracle Database 10g activities store their objects in this sysaux tablespace. This is mandatory as a database is created. The Oracle Enterprise Manager (OEM) Grid Control repository used to go in its own oem_repository tablespace, but with Oracle Database 10g its objects now reside in sysaux.
As the dbca does its thing, a tablespace is created that serves as the default location for intermediary objects Oracle Database 10g builds as it processes SQL statements. SQL stands for the structured query language, an industry standard in the database arena, used to retrieve, create, change, and update data. Most of the work Oracle does to assemble a result set for a query operation is done in memory. A result set is a collection of data that qualifies for inclusion in a query passed to Oracle. If the amount of memory allocated for query processing is insufficient to accommodate all the activities required to assemble data, Oracle uses this default temporary tablespace as its secondary work area for many activities including sorting.
As sessions interact with the Oracle Database 10g, they create, change, and delete data. Undo is the act of restoring data to a previous state. Suppose one's address is changed from 123 Any Street to 456 New Street via a screen in the personnel application.
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