Network Deployment (Distributed operating systems), v8.0 > Set up the application serving environment > Administer application servers

Manage shared libraries

Overview

Shared libraries are files used by multiple applications. Each shared library consists of...

• Symbolic name
• Java class path
• Native path for JNI

We can use shared libraries to reduce the number of duplicate library files on the system.

Your applications use the same library files. The applications already are deployed on a server or you currently are deploying the applications.

Suppose that we have four applications that use the same library file...

my_sample.jar

Instead of having four copies of my_sample.jar on the system after the four applications are deployed, you can define a shared library for my_sample.jar and have the four deployed applications use that one my_sample.jar library file.

Isolated shared libraries provide another way to reduce the number of library files. Isolated shared libraries each have their own class loader, enabling a single instance of the classes to be shared across the applications. Each application can specify which isolated shared libraries that it wants to reference. Different applications can reference different versions of the isolated shared library, resulting in a set of applications sharing an isolated shared library. With isolated shared libraries, some applications can share a single copy of Library A, v1 while other applications share a single copy of Library A, v2, for a total of two instances in memory.

Using the admin console, you can...

1. Define shared libraries for the library files that multiple applications use
2. Associate the libraries with specific applications or modules or with an application server

Guidelines for associating shared libraries are as follows:

• Associate a shared library file with an application or module to load the classes represented by the shared library in a local class loader, which can be an application-wide or module-wide class loader.

• Associate an isolated shared library file with an application or module to load the classes represented by the shared library in a separate class loader created for that shared library.

• Associate a shared library file with a server to load the classes represented by the shared library in a server-wide class loader. This class loader is the parent of the application class loader, and the WAS extensions class loader is its parent. Associating a shared library file with a server associates the file with all applications on the server.

• Do not associate an isolated shared library file with a server if you want a separate class loader for a shared library. If you associate the shared library with a server, the product ignores the isolation setting and still adds files in the shared library to the application server class loader. That is, associating an isolated shared library file with a server associates the file with all applications on the server. The product does not use an isolated shared library when you associate the shared library with a server. Associate an isolated shared library with an application or module.

Instead of using the admin console to associate a shared library with an application, you can use an installed optional package. You associate a shared library to an application by declaring the dependent library .jar file in the MANIFEST.MF file of the application.

Procedure

1. Use the admin console to define a shared library.

   1. Create a shared library.

      On a single-server product, you can define a shared library at the cell, node, or server level.

      On a multiple-server product, you can define a shared library at the cell, node, server, or cluster level.

      Define a library at one of the these levels does not automatically place the library into a class loader. We must associate the library with an application, module, or server before the product loads the classes represented by the shared library into a local or server-wide class loader.

   2. Associate each shared library with an application, module, or server.

      • Associate a shared library with an application or module that uses the shared library file.

        If you enabled the Use an isolated class loader for this shared library setting when creating the shared library, associate the isolated shared library with an application or module to use a separate class loader for the shared library.

      • Associate a shared library with an application server so every application on the server can use the shared library file.

2. Use an installed optional package to declare a shared library for an application.

3. Remove a shared library.
   Environment | Shared libraries | library | Delete

Related

Create shared libraries
Shared library collection
Associate shared libraries with applications or modules
Associate shared libraries with servers
Installed optional packages
Use installed optional packages
Library reference collection
Class loaders
Configure native libraries in shared libraries
Shared library settings

+

Search Tips   |   Advanced Search