Database Structure of oracle Architecture

Oracle architecture database structure oracle database consists of two parts: database and instance database: a series of physical files that specifically store data and related objects. Instance: refers to a series of operating system processes and the memory zone (SGA) it manages ). The storage structure of oracle databases is also divided into two categories: physical storage structure and logical storage structure. The physical storage structure corresponds to a series of files of different formats, types, and functions, which are used to store objects and physical data. The logical structure is the way in which data is stored and managed in oracle. The physical storage structure of the www.2cto.com database is divided into four types of Files based on different data processing and tasks: 1. control Files; 2. datafiles ); 3. Temporary files (tempfiles); 4. online redolog Files & Archived Log files) Control Files: a binary file that cannot be directly modified using a text editing tool, generally, the content in this file is maintained by oracle. An oracle database must have at least one control file. However, we recommend that you have at least two redundant files stored on different disks to improve the availability of the file. Data File: the place where the actual data is stored in the database. A tablespace (a tablespace is a logical structure, and a database contains multiple tablespaces) may have multiple data files, but one data file only belongs to one tablespace. Temporary File: a temporary file is not a temporary file, but a data file corresponding to the tablespace. In terms of actual performance, it does not mean that the file will be deleted when it is used up, the object stored in the file is a temporary object. The temporary tablespace data file is a sparse type of file. during initial creation, it only seems to occupy the specified size of space, but the space is not actually occupied at this time, the space of such files will be allocated in actual use. Www.2cto.com log file (redolog files): record the operations performed on the database and redo log files first. Logical Structure: 1, Block 2, Zone 3, segment 4, tablespace block: The smallest storage unit in the oracle logical Storage Structure: The smallest allocation unit in the oracle database, there is a group of continuous blocks: it consists of a series of zones. A short table space only belongs to a specific storage object: The largest logical storage unit in the database, colleagues are also the logical units directly associated with the physical structure of the database. Each tablespace is composed of one or more (up to 1023) data files (data files in the physical storage structure. Objects Created in the database are stored in the specified tablespace, and even one object may have multiple tablespaces.