Shulou(Shulou.com)06/01 Report--

11 、 JServer JAVA Virtual Machine

JVM is the cornerstone of Java technology, which is responsible for realizing the independence of Java hardware and operating system, protecting user machines from malicious code, and making the compiled code of Java small enough.

The compiled code is small enough to facilitate dissemination on the Internet, but it is mainly aimed at Java Applet, that is, when you need to download the Java compiled code on the client side and run it.

You have to consider the size of the files you need to download. This problem is not so prominent in the Java enterprise Bamp S mode.

JVM is an abstraction layer on top of different hardware and operating systems. Like OS, it defines the instruction set and manages its own memory area. Java runs on this layer of abstraction.

JVM shields Java from the differences between the underlying hardware and operating system, which realizes the independence of the platform. At the same time, because Java runs on JVM, JVM controls the behavior ability of Java like a sandbox.

It can also prevent malicious code from infringing the underlying OS. In fact, it is the security of JVM that limits the behavior ability of Java.

Description: JVM and Jserver

-

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:

-

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:

-

SYS

How to Install and De-Install:

-

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:

-

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:

-

Overview of the Java Virtual Machine (JVM)

12 、 Oracle XDK

The Oracle XDK component is a versatile collection of components that can be built and deployed to handle XML. Oracle XDK provides the foundation for XML's solution.

XDK supports XML DB,XDB as a collection of technologies that can be used to store and process XML in DB. We can use XDK and XDB to build applications that run in DB, or we can use XDK alone.

Description:

-

Oracle Oracle XML Developer's Kit (XDK) is a versatile set of components that enables you to build and deploy C, Clearing, 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:

-

SYS: In 9.2XDK should be installed in SYS schema, as 9.2.0.* patchsets upgrade XDK installed in SYS schema only.

How to Install and De-Install:

-

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:

-

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:

-

Oracle XML DB Developer's Guide, 10g Release 2

13. RAC (Oracle Real Application Clusters)

This is the component we are most familiar with, and it is also the component that must be installed when installing the cluster.

Oracle Real Application Clusters achieves high utilization of standard, low-cost, modular server clusters such as blade servers. RAC provides automatic load management for services. A service is a group or class of applications

They consist of business components that correspond to the load of the application. Services in RAC implement continuous, uninterrupted database operations and support multiple services in multiple instances.

Assign the service to run on one or more instances and alternative instances that can be used as backup instances. If the primary instance fails, Oracle will transfer the service from the failed instance to the alternative instance that is still running.

Oracle also automatically balances the connection load between the instances running the service.

RAC uses multiple low-cost computers to work together as a mainframe computer for database processing, which is the only feasible alternative to large-scale SMP systems and can be used in a variety of applications.

RAC based on shared disk architecture can be expanded and shrunk as needed without having to partition data manually between cluster servers. RAC provides the ability to add and remove servers to and from the cluster with one click.

Therefore, you can easily provide a server to or remove a server from the database.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.