This chapter describes the nature of and relationships among logical storage structures. These structures are created and recognized by Oracle Database and are not known to the operating system.
5一般来说,一个数据库只能被一个实例访问,这种模式叫做单实例数据库(Single Instance Database)。但是,在某些情况下,一个数据库可以被多个实例访问,这种模式叫做多实例数据库(Multi Instance Database),也叫做Oracle Real Application Clusters(RAC)。RAC是Oracle数据库的一种高可用性和高性能的解决方案,它可以实现数据...
You can create as many schemas as necessary for your database. For example, you could create a schema for each database user. However, schemas and users are not synonymous as they are in Oracle. By default, only a superuser can create a schema or give a user the right to create a ...
This chapter includes the following sections: Figure 2-1
database design process. At this stage, designers focus on understanding the problem domain and defining the overall structure of the database without getting into technical implementation details. The primary goal is to create a clear and comprehensive representation of the data and its re...
An example of in-product physical data modeling. Source: https://docs.oracle.com/cd/E13167_01/aldsp/docs25/samples_tutorial/modeling.html. Key Physical Data Model Characteristics: Specificity. Physical data models are highly specific, detailing the database schema’s structure and components. DBMS...
Oracle's data dictionary is composed of views. It stores all data about theOracle databasein tables, but disallows direct access to the tables instead of providing views through which the user can only select data. Normally the views are created usingSQLstatements. ...
In SQL, all logical operators evaluate toTRUE,FALSE, orNULL(UNKNOWN). In MySQL, these are implemented as 1 (TRUE), 0 (FALSE), andNULL. Most of this is common to different SQL database servers, although some servers may return any nonzero value forTRUE. ...
A logical model adds more structure by defining data elements, attributes, and their relationships. A physical model addresses implementation details, specifying how data will be stored in a database’s tables, columns, and indexes. Here’s how to think of each model in the simplest terms: ...
others. For example, some processors can perform high I/O tasks such as database operations very quickly while others may be better at handling a high number of simultaneous users. Make sure that you pay close attention to this aspect of your server options before making a processor ...