VAXDBMS 是 VAX 数据库系统的核心。它由下述三部分组成:一、语言部分(一)、DDL 语言1.模式数据描述语言,它用于描述全局的数据逻辑结构。2.子模式数据描述语言,它用于描述局部的数据逻辑结构。3.物理数据描述语言,它用于描述数据的存贮模式。4.安全模式描述语言,它用于控制 DML 语句的执行。 VAXDBMS is the core of the VAX database system. It consists of the following three parts: First, the language part (A), DDL language 1. Schema data description language, which is used to describe the global data logic structure. 2. Sub-pattern data description language, which is used to describe the local data logic structure. 3. Physical data description language, which is used to describe the data storage mode. 4. Security Model Description Language, which is used to control the execution of DML statements.