oracle 基础知识三

你的名字 2022-09-27 04:53 273阅读 0赞

oracle体系结构

oracle数据库通常采用的是三级模式、二级映像结构。即外模式、模式、内模式；外模式/模式映像，模式/内模式映像。

**模式schema也称为逻辑模式**，是数据库中全体数据的逻辑结构和特征描述，是所有应用程序的公共数据结构。模式的特点：

a、）一个数据库有且只有一个模式，它统一的、综合地考虑所有用户的需求，并将这些有机的组成一个逻辑整体。

b、）模式是逻辑的，它与具体的应用程序无关或不属于某个应用程序。它描述的是一个数据库的总体结构，是装配数据的一框架。

c、）模式是以某种数据模型为基础的。定义模式时不仅要定义数据的逻辑结构，而且还要定义这些数据项之间的联系，定义与数据项有关的安全性、完整性等。

d、）模式设计是数据库设计的重要任务。

**外模式 external schema 也称为用户模式**，是数据库用户（应用程序、终端用户）能够看见何使用的局部数据的逻辑结构和特征描述，是用户所用的数据库结构。它的特点：

a、）一个数据库具有多个外模式，分别对应于每个用户。

b、）外模式是保证数据库完全性的一个有力措施。每个用户只能看见和访问所对应的外模式中的数据，而看不见其他数据。

c、）可以通过授权的方式，使一个用户可以使用另一个用户的外模式。

**内模式 internal schema 也称为存储模式**，是对数据的物理结构和存储方式的描述，是数据在数据库内部的表示方式，是整个数据库底层结构的表示，是数据库在物理存储方面的描述。其特点：

a、）一个数据库有且只有一个内模式。

b、）一个数据库由多个文件组成。

c、）内模式对用户是透明的。

d、）内模式不同于物理层。它只是一个描述（数据是否压缩、加密；存储方式是按顺序、B树结构、Hash方法；按照什么样的方式组织索引；记录的结构有何规则等）。

在ORACLE数据库中，模式对应整个数据库中的表、索引、序列；外模式对应某个用户的表、索引、序列、视图、同义词，也称为“方案对象”；内模式对应存储结构，比如逻辑存储结构（表空间、区、段、块等）、物理存储结构（数据文件、控制文件、重做日志文件、初始化参数文件、配置文件等）。

二级映像

二级映像保证了数据库的数据独立性。

外模式/模式映像：指由模式生成外模式的规则，定义了各个外模式和模式之间的对应关系。其特点：

a、）一个数据库可以有多个外模式/模式映像。对应于一个模式可以有多个外模式，所以每个外模式都有一个外模式/模式映像。

b、）给数据库提供了逻辑独立性。逻辑独立性是指应用程序和数据的逻辑结构之间是相互独立的，即当模式放生变化（表增删字段或增加新表）时，只要数据库管理员对相应的外模式/模式映像做相应的修改，就可以使外模式保持不变。

模式/内模式映像：指模式在物理设备中的存储结构，定义了模式和内模式之间的对应关系。其特点：

a、）一个数据库只有一个模式/内模式映像。因为数据库只有一个模式和内模式。

b、）给数据库提供了物理独立性。指应用程序和存储在磁盘上的数据库中的数据是相互独立的。即，数据在磁盘上的数据库中如何存储完全由DBMS来管理，应用程序不需要了解，只需要了解数据的逻辑结构就可以了。

oracle数据库的存储结构分为 逻辑存储结构和物理存储结构，他们是相互独立又相互联系的。

逻辑存储结构主要描述ORACLE数据库的内部存储结构，即描述的是在oracle数据库中如何组织、管理数据，逻辑存储结构和平台是无关，是由oracle数据库定义、创建和管理。

物理存储结构主要描述ORACLE数据库的外部存储结构，即描述的是在操作系统中如何组织、管理数据。物理存储结构和平台是有关的。

从物理上看，数据库是由控制文件、数据文件、重做日志文件、初始化参数文件等操作系统文件组成。从逻辑上看是由 表空间（系统表空间和用户表空间）组成。表空间是最大的逻辑单位，接下来是，段、区、块。表空间可以理解为存储数据用的数据文件的一个分类。块是最小的逻辑单位，是数据管理的单位，即数据管理中输入输出的最小单位。逻辑存储结构中的块对应于操作系统中的块。

多个块组成区；多个区组成段；多个段组成表空间；多个表空间组成逻辑数据库。

一个区只能在一个数据文件中，一个段中的各个区可以分别在多个数据文件中。组成区的块是连续的。

表空间 tablespace 一个表空间可以包含多个数据文件，但以个数据文件只能属于一个表空间。任何方案对象被逻辑地存储在表空间中，同时又被物理地存储中数据文件中。方案对象的定义被存储中不同于存储其他数据的表空间system中。一个用户的不同方案对象的数据可以被存储在不同的表空间中。数据库、数据文件、表空间、方案对象的关系是：数据库包含表空间，表空间又包含数据文件，数据文件又包含方案对象，方案对象又可以同时属于不同的数据文件中。

段：用于存储表空间中某一种特定的、具有独立存储结构的数据库对象的数据，它由一个或多个联系的区组成。当创建表、索引、簇等对象时，oracle就会为这些对象分配存储空间（段）。段分为：表段、表分区段、索引段、索引分区段、临时段、回退段、撤销段、二进制大对象段（如果数据长度少于4000字节，则与其他列数据会一起存放在表段中；否则数据就会被存放到二进制大对象段中）。

段类型

**进程结构**

**  ** 进程包括：用户进程、oracle进程。oracle进程有包括：服务器进程、后台进程。服务器进程又分为：专用服务器进程和共享服务器进程。

服务器进程为客户端的用户进程提供服务。用户进程必须通过服务器进程才能访问数据库。服务器进程的任务是：

a、）解析并执行用户提交的SQL语句；

b、）搜索SGA区的数据库缓存，决定是否读取数据文件。如果数据块不在SGA区的数据库缓存中，则将其从数据文件中读入；

c、）将查询或执行后的结果或错误信息返回给用户。

后台进程：ORACLE将管理和操作复杂数据块的任务划分，分别由几个相互独立的、各就其职的后台进程来分工合作，共同完成任务。后台进程的任务：

a、）在内存和外存之间进行I/O操作；

b、）监视各个进程的状态；

c、）协调各个进程的任务；

d、）维护系统的性能；

e、）保证系统的可靠性；

主要的后台进程：

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 <tr style="mso-yfti-irow: 7;"> 
 <td style="border-bottom: black 1pt solid; border-left: black 1pt solid; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 225.15pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1;"> Recoverer <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">恢复进程 </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 106.3pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> RECO </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 94.65pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">可选 </td> 
 </tr> 
 <tr style="mso-yfti-irow: 8;"> 
 <td style="border-bottom: black 1pt solid; border-left: black 1pt solid; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 225.15pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1;"> Lock&nbsp; <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">锁进程 </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 106.3pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> LCKn </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 94.65pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">可选 </td> 
 </tr> 
 <tr style="mso-yfti-irow: 9;"> 
 <td style="border-bottom: black 1pt solid; border-left: black 1pt solid; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 225.15pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1;"> Recovery writer&nbsp; <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">闪回恢复写进程 </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 106.3pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> RVWR </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 94.65pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">可选 </td> 
 </tr> 
 <tr style="mso-yfti-irow: 10;"> 
 <td style="border-bottom: black 1pt solid; border-left: black 1pt solid; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 225.15pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1;"> Change tracking writer <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">闪回变化跟踪写进程 </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 106.3pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> CTWR </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 94.65pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">可选 </td> 
 </tr> 
 <tr style="mso-yfti-irow: 11;"> 
 <td style="border-bottom: black 1pt solid; border-left: black 1pt solid; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 225.15pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1;"> Job queue monitor <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">作业队列监视进程 </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 106.3pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> CJOn </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 94.65pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">可选 </td> 
 </tr> 
 <tr style="mso-yfti-irow: 12;"> 
 <td style="border-bottom: black 1pt solid; border-left: black 1pt solid; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 225.15pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1;"> Job queue&nbsp; <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">作业队列进程 </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 106.3pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> Jnnn </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 94.65pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">可选 </td> 
 </tr> 
 <tr style="mso-yfti-irow: 13;"> 
 <td style="border-bottom: black 1pt solid; border-left: black 1pt solid; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 225.15pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1;"> Dispatcher <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">调度进程 </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 106.3pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> Dnnn </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 94.65pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">可选 </td> 
 </tr> 
 <tr style="mso-yfti-irow: 14; mso-yfti-lastrow: yes;"> 
 <td style="border-bottom: black 1pt solid; border-left: black 1pt solid; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 225.15pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1;"> Shared server <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">共享服务器进程 </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 106.3pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> Snnn </td> 
 <td style="border-bottom: black 1pt solid; border-left: #f0f0f0; padding-bottom: 0cm; background-color: transparent; padding-left: 5.4pt; width: 94.65pt; padding-right: 5.4pt; border-top: #f0f0f0; border-right: black 1pt solid; padding-top: 0cm; mso-border-alt: solid black .5pt; mso-border-themecolor: text1; mso-border-left-alt: solid black .5pt; mso-border-left-themecolor: text1; mso-border-top-alt: solid black .5pt; mso-border-top-themecolor: text1; mso-border-bottom-themecolor: text1; mso-border-right-themecolor: text1;"> <span style="font-family: 宋体; mso-ascii-font-family: Calibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: Calibri; mso-hansi-theme-font: minor-latin;">可选 </td> 
 </tr> 
 </tbody> 
</table>

简写的进程名中的n表示根据任务的多少，该进程可以有多个正在运行。Oracle最多可以启动10个归档进程（ARC0，ARC1，ARC2…ARC9）。Orace最多可以有10个锁进程（LCK0，LCK1…LCK9）