I. Basic Concepts
1) physical structure data files, control files, log files, parameter files, and backup files constitute the physical storage structure of the Oracle database.
Control file management and control data files and log files 0. The parameter files and backup files are under the database directory. The path of the control file is not a component of the database file. The parameter file is used to find the control file. 1. Data Files (. DBF,. dat) an Oracle database can have multiple data files. The data file contains all the database data. Data in the logical database structure is also stored in data files. A database file can belong to only one database; A database file can be set to auto scaling; a tablespace (logical unit of database storage) can have one or more data files. The data between the data file and the memory is interacted with by the Oracle background process dbwr. The size of the data file is expressed by byte and data block. The size of the data block is determined by the db_block_size parameter. 2. control file (. CTL) A database has a control file, which is used to maintain the global physical structure of the database and supports successful data startup and operation. Control File Content: database Name, database data file and log file name and location, database creation date, log history, archived log information, tablespace information, offline data file range, data file copy information, backup combination and backup block information, backup data file and redo log information, current log sequence number, checkpoint information. 3. log files (. Log) are online (redone) log files used for database fault and database recovery. Archiving log files 4. when opening the database, the file uses the sequential physical structure (file structure): parameter file ---> Control File ------> data file ------> Log File 5. run the command to view the file information DESC v $ controlfileselect status, name from V $ controlfile; DESC v $ datafileselect file #, name from V $ datafile; desc v $ logfileselect member from V $ logfile; 6. In addition to the preceding three data dictionaries, there are also V $ instancev $ controlfilev $ datafilev $ logfilev $ logv $ databasev $ log_history 2) memory Structure 1. each Oracle instance in SGA corresponds to an sga1) dbbuffer database high-speed buffer. Reserved Buffer Pool: default buffer pool of the code table: recycled Buffer Pool: large tables with frequent access 2) large shared area 3) The shared pool has a great impact on database performance. A) database Buffer: B) Dictionary Buffer: 4) Redo buffer5) fixed sga2. 3) Logical Structure 1. Block: The default value is 8 KB, which can be set. An integer multiple of the operating system block size. 2. Disk Area 3, segment 4, tablespace a database usually contains three default tablespaces: system, sysaux, and temp, one or more temporary tablespaces, one undo tablespace, and several application-specific tablespaces. You can create new tablespaces. You need to specify the type. 5. Data Files
