oracle基本概念之–oracle的邏輯結構和物理結構

1、資料庫的邏輯結構和物理結構：
   Oracle logically divides the database into a smaller units to manage ,store,and retreive
data efficently.
  Tablespace/Blocks/Extents/segment/
有四種segment:
data segment、Index segment、Temporay segment、Rollback Segment
temporary segment:
Are created when Oracle needs a temporary work area,such as for sorting,during a query,
to complete execution of a SQL statement.These segments are freed when the execution completes.
Rollback segment：Used to store undo information.When you roll back the changes madde to the
database,the information in the rollback segment is used to undo the changes.
 
   The physical daabase structure consists of three types of physcial files
   data files
   control files
   redo log files

The control file contains the database name and timestamp of database creation as well as the name and location of every data file and redo log file.