Application servers, nodes, and
cells:-
Application Servers:-
The application server is the primary runtime component in all
configurations and is where an application actually executes. All
WebSphere Application Server configurations can have one or more
application servers. In the Express and Base configurations, each
application server functions as a separate entity. There is no
workload distribution or central administration among 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.
Nodes, node
groups, and node agents:-
A node is a grouping of application servers for configuration and
operational management on one machine. Nodes are generally associated
with a physical machine. It is possible to have multiple nodes on a
single machine, but nodes cannot span machines. In a stand-alone
application server environment, there is
only one node. With Network Deployment, you can configure multiple
nodes in a distributed server environment that are managed from one
central administration server.
In centralized management configurations, each node has a node agent
that works with the deployment manager to manage administration
processes. The nodeagent is created under the covers when you
federate a stand-alone node to a cell.
A node group is a grouping of nodes within a cell that have similar
capabilities. A node group validates that the node is capable of
performing certain functions.
Cells:-
A cell is a grouping of nodes into a single administrative
domain. In the Base and Express configurations, a cell contains one
node and that node contains one application server.
In a distributed server configuration, a cell can consist of multiple
nodes, which are all administered from a single point (the 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.
Federation:-
Federation
is a kind of process to manage the deployment manager profile with
either AppServer profile or Custom profile for administration. Once
we add a node to the deployment manager we can create number of
servers under that node. So, we can have a single point of
administration and we can have a clustered environment. Without
federation we cannot create the clusters. At the time of federation
nodeagent will be created to communicate between deployment manager
and the federated profile.
Servers:-
WebSphere
Application Server supplies application servers, which provide the
functions that are required to host applications and proxy servers
that distribute work to the application servers. It also provides the
ability to define external servers to the administration process.
Application servers
provide the runtime environment for application code. They provide
containers and services that specialize in enabling the execution of
specific Java application components. Each application server runs in
its own Java Virtual Machine (JVM).
