Oracle 數據庫 組件相關說明【第三部分】
11、JServer JAVA Virtual Machine
JVM是Java技術的基石，它負責實現Java的硬件和操作系統的獨立性，保護用戶機器不被惡意代碼侵害，同時使Java的編譯代碼足夠小。
編譯出來的代碼足夠小是為了方便在網上傳播，其實主要是針對Java Applet的，也就是當你需要在客戶端下載Java編譯后的代碼然后運行的時候就
不得不考慮需要下載的文件的大小了。在Java企業級B/S模式下這個問題不是那么突出。
JVM是在不同的硬件和操作系統之上的一個抽象層。它如同OS一樣定義了指令集，并管理自己的內存區。Java就運行在這個抽象層之上，
JVM對Java屏蔽了底層硬件和操作系統的不同，這就實現了平臺的獨立性。同時因為Java運行在JVM上，JVM就像一個沙箱一樣控制著Java的行為能力，
也就可以避免惡意的代碼侵害底層的OS。其實就是JVM的安全性對Java的行為能力做了限制。
Description: JVM and Jserver
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JVM is a platform-independent execution environment that converts Java bytecode into machine language and executes it.
Most programming languages compile source code directly into machine code that is designed to run on a specific microprocessor architecture or
operating system, such as Windows or UNIX. A JVM -- a machine within a machine -- mimics a real Java processor, enabling Java bytecode to be
executed as actions or operating system calls on any processor regardless of the operating system. For example, establishing a socket connection
from a workstation to a remote machine involves an operating system call. Since different operating systems handle sockets in different ways,
the JVM translates the programming code so that the two machines that may be on different platforms are able to connect.
Oracle JServer Option is a Java Virtual Machine (Java VM) which runs within the Oracle database server's address space.
Oracle also provides a JServer Accelerator to compile Java code natively. This speeds up the execution of Java code by eliminating interpreter overhead.
What is NCOMP:
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The Java language was designed for a platform-independent, secure development model. Translating Java bytecodes into machine instructions degrades performance.
To regain some of the performance loss, you may choose to natively compile certain classes. For example, you may decide to natively compile code with CPU
intensive classes and this can be achived using NCOMP. In 10g one can install NCOMP from companion CD if they are really using JAVA intensive
application and facing any performance issues because of the reason given above.
Note.134985.1 How to use JServer Accelerator and the NCOMP Utility
Schema:
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SYS
How to Install and De-Install:
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Note.153271.1 How to manually install JVM into 8i database
Note.126029.1 How to Remove the Jserver (JVM) in versions 8.1.5 and 8.1.6 of the rdbms
Note.175472.1 How to Reload the JVM in 8.1.7.X
Note.202914.1 How to Reload the JVM in 9.0.1.X
Note.209870.1 How to Reload the JVM in 9.2.0.X
Note.276554.1 How to Reload the JVM in 10.1.0.X and 10.2.0.X
Note.457279.1 How to Reload the JVM in 11.1.0.x
Note.1112983.1 How to Reload the JVM in 11.2.0.x
FAQ:
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Note.156439.1 How Does Oracle Store Java Casses Into Database
Note.265293.1 How To Find The Java Source Of A Java Stored Procedure
Note.397770.1 How to Correctly Check if the Oracle JVM is Installed in the Database
Note.471867.1 Simple Java Stored Procedure to Check that the Oracle JVM is Operating Correctly
Note.1098505.1 Master Note for Oracle JVM
Documentation:
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Overview of the Java Virtual Machine (JVM)
12、Oracle XDK
Oracle XDK 組件是一個多功能集合的組件，其可以構建和部署C，C++，Java 程序來處理XML。Oracle XDK 為XML的解決方案提供了基礎。
XDK 支持XML DB，XDB是一個技術的集合，其可以用來在DB中存儲和處理XML。 我們可以使用XDK 和XDB來構建應用在DB中運行，也可以單獨使用XDK。
Description:
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Oracle Oracle XML Developer's Kit (XDK) is a versatile set of components that enables you to build and deploy C, C++, and Java software
programs that process XML. You can assemble these components into an XML application that serves your business needs.
Oracle XDK provides the foundation for the Oracle XML solution. The XDK supports Oracle XML DB, which is a set of technologies used for
storage and processing of XML in the database. You can use the XDK in conjunction with Oracle XML DB to build applications that run in
Oracle Database. You can also use the XDK independently of XML DB.
The Oracle XDK is fully supported by Oracle Corporation and comes with a commercial
redistribution license.
The standard installation of Oracle Database includes the XDK.
Note:
Customers using Oracle XDK with PL/SQL and migrating from Oracle Database Release 8.1 or 9.2 are strongly encouraged to use AL32UTF8 as
the database character set. Otherwise, issues can arise during PL/SQL processing of XML data that contains escaped entities.
9206 XDK should be installed in 9204 database, 9207 XDK should be installed in 9205 database and 9208 XDK should be installed in 9206 server.
That is why in 9.2.0.8 installation you will see XDK version 9.2.0.10
Schema:
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SYS: In 9.2 XDK should be installed in SYS schema, as 9.2.0.* patchsets upgrade XDK installed in SYS schema only.
How to Install and De-Install:
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There is no need to install XDK Java in 10g database as it comes with XDB schema. In 10g, much about XDK has been included in Oracle XML Database (XDB).
Note.317176.1 How to De-install corrupted pl/sql XDK in 9.2 and Install the right version
Note.435999.1 How To Install XDK 10.2.0.x ?
Note.277152.1 How to install XDK 9.2.0.x in an 8.1.7 Database Cleanly
Note.453050.1 How to Verify the XDK Installation
Installing the XDK (11gR2) :
Note.437266.1 Reloading the XDK for Java In the Database
FAQ:
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Note 250288.1 XDK For PL/SQL API Has Been Deprecated from 9.2 Database
Note.103871.1 XML Parser for PL/SQL FAQs
Note.103872.1 XML Parser for Java Version 2 - Frequently Asked Questions
Documentation:
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Oracle XML DB Developer's Guide, 10g Release 2 (10.2)
13、RAC(Oracle Real Application Clusters)
這是我們最熟悉的組件了，也是安裝集群時一定會安裝的組件
Oracle Real Application Clusters 實現了標準的、低成本、模塊化
服務器（如刀片服務器）集群的高利用率。RAC 為服務提供了自動負載管理。服務是一組或一類應用程序，
它們由與應用程序負載相對應的業務組件組成。RAC 中的服務實現了連續、不中斷的數據庫操作，并支持多個實例中的多個服務。
將服務分配在一個或多個實例以及可以用作備份實例的替代實例上運行。如果主實例出現故障，Oracle 將把服務從故障實例轉移到仍舊運行的替代實例上。
Oracle 還自動在運行著服務的實例間進行連接負載平衡。
RAC 利用多臺低成本計算機一同工作，作為一臺大型計算機來進行數據庫處理，這是大型 SMP 系統唯一可行的替換方案，可用于各種應用程序。
基于共享磁盤架構的 RAC 可以根據需要擴大和縮小，而不必在集群服務器之間采用人工方式對數據進行分區。RAC 提供了一鍵式向集群中添加服務器和從中刪除服務器的功能。
因此，可以輕松地向數據庫提供服務器或從中刪除服務器。
