In this section, you will
learn about commonly used WebSphere Application Server architectural terms.
Application Server
According to the WebSphere Application Server Glossary, an application server is "a server program in a distributed network that provides the execution environment for an application program."
More specifically:
The application server is the primary run-time component in all configurations and is where an application actually executes. All WebSphere Application Server configurations can have one or more application servers. With Network Deployment, you can build a distributed server environment consisting of multiple application servers maintained from a central administration point. In a distributed server environment, you can cluster application servers for workload distribution.
The following diagram shows one possible architecture of a
WebSphere Application Server environment:
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Below, you will find definitions for each of the terms shown in
the graphic above.
Cell
The WebSphere
Application Server Glossary defines a cell as: "A group of managed
processes that are federated to the same deployment manager and can include
high-availability core groups." The IBM Redbooks publication WebSphere
Application Server V7: Concepts, Planning, and design provides the following,
more detailed, explanation:
A cell is a grouping of nodes into a single administrative
domain. ... In a Network Deployment environment, a cell can consist of multiple
nodes (and node groups), which are all administered from a single point, the
deployment manager. If your cell configuration contains nodes running on the
same platform, it is called a homogeneous cell. It is also possible to have a
cell made up of nodes on mixed platforms. This is referred to as a
heterogeneous cell.
Cluster
A cluster is
defined as "a group of application servers that collaborate for the
purposes of workload balancing and failover" in the WebSphere Application
Server Glossary.
In other words:
A cluster is a
logical collection of application server processes that provides workload
balancing and high availability. Application servers that belong to a cluster
are members of that cluster and must all have identical application components
deployed on them. Other than the applications configured to run on them,
cluster members do not have to share any other configuration data. For example,
one cluster member might be running on a large multi-processor server while
another member of that same cluster might be running on a small mobile
computer. The server configuration settings for each of these two cluster
members is very different, except in the area of the application components
that are assigned to them. In that area of configuration, they are identical.
The members of a cluster can be located on a single node (vertical cluster),
across multiple nodes or on a combination of the two. When you install, update,
or delete an application, the updates are automatically distributed to all
members in the cluster.
Deployment Manager
A Deployment
Manager is "a server that manages operations for a logical group or cell
of other servers," as stated in the WebSphere Application Server Glossary.
A more detailed explanation is that the deployment manager is:
the central
administration point of a cell that consists of multiple nodes and node groups
in a distributed server configuration. ... The deployment manager uses the node
agent to manage the application servers within one node. A deployment manager
provides management capability for multiple federated nodes and can manage
nodes that span multiple systems and platforms. A node can only be managed by a
single deployment manager and must be federated to the cell of that deployment
manager. The configuration and application files for all nodes in the cell are
centralized into a master configuration repository. This centralized repository
is managed by the deployment manager and synchronized with local copies that
are held on each of the nodes.
Node
As defined in the
WebSphere Application Server Glossary, a node is "a logical grouping of
managed servers."
In particular:
A node is an
administrative grouping of application servers for configuration and
operational management within one operating system instance (virtualization
allows multiple operating systems on one machine). It is possible to create
multiple nodes inside one operating system instance, but a node cannot leave
the operating system boundaries. In a stand-alone application server
configuration, there is only one node. With Network Deployment, you can
configure a distributed server environment consisting of multiple nodes, which
are managed from one central administration server.
Node Agent
A Node Agent is
"an administrative agent that manages all application servers on a node
and represents the node in the management cell" according to the WebSphere
Application Server Glossary
In addition:
In distributed
server configurations, each node has a node agent that works with the
deployment manager to manage administration processes... A node agent is
created automatically when you add a stand-alone node to a cell. It is not included
in the Base and Express configurations.
In simpler terms, the node agent's purpose is to pass information
between the deployment manager and the application server.
Here we have a brief explanation of IBM WebSphere Application Server in this video,
Profile
A profile is "an instance of a WebSphere Application Server
configuration."
More specifically:
Profiles are
collections of user files. They share core product files. A profile contains
its own set of scripts, its own environment, and its own repository. Each
profile is stored in a unique directory path selected by the user at profile
creation time. Profiles are stored in a subdirectory of the installation
directory by default, but they can be located anywhere. WebSphere Profiles were
introduced in WebSphere Application Server v6.0. One main advantage of profiles
is that they allow an administrator to have multiple application servers on a
single machine that all use the same binaries from one install of WebSphere
Application Server.
Administration is greatly enhanced when using
profiles instead of multiple product installations. Not only is disk space
saved, but updating the product is simplified when you maintain a single set of
product core files. Also, creating new profiles is more efficient and less
prone to error than full product installations, allowing a developer to create
separate profiles of the product for development and testing.
