Why and when to perform this task
In WebSphere Application Server for z/OS, the functional component
on which applications run is called a server. Servers comprise address
spaces that actually run code.

Within each server are two kinds of address spaces:
controllers and servants. A controller runs system authorized programs
and manages tasks, such as communication, for the server. Each server has
one controller that you start with a JCL start procedure when you enter the
appropriate start command on the MVS console.
A servant is the
address space in which the JVM resides. It runs unauthorized programs such
as business applications. Depending on the workload, a server has one or more
servants running at a time. When work builds up, WLM dynamically starts additional
servants to meet the demand.
Note: The
location service daemon, node agent and JMS server are specialized servers
and have no servants.
Here is a quick breakdown of the different
server types on your system:
- Unmanaged (base) Application Server
- The Application Server that was set up during base configuration that
hosts your J2EE applications.
- Managed (Network Deployment) Application Server
- The Application Server set up during Network Deployment configuration
that hosts your J2EE applications.
- Location service daemon
- A server which is the initial point of contact for client requests in
either configuration.
- JMS server
- Hosts the JMS function in the WebSphere Application Server for z/OS, which
controls the MQ broker and queue manager in either configuration.
- Deployment manager
- A specialized Application Server that hosts the administrative console
application (it hosts only administrative applications) and provides cell-level
administrative function in a Network Deployment configuration. The administrative
console application administers servers (grouped into nodes) on many different
systems. The deployment manager is the sole occupant of its own node structure
which does not need a node agent because there are no Application Servers
in the node, and a cell may have only one deployment manager.
Note: The version
of the administrative console application that runs in the deployment manager
is designed to manage multinode environments, whereas the version in the base
Application Server is for single node environments only.
- Node agent
- Provides node-level administrative function in a Network Deployment configuration.
Note: Every element of the configuration (servers,
clusters, nodes and cells) has both a long and short name:
- The "Server name" is the server long name used in the HFS path and the
principal name by which the server is known to WebSphere Application Server
for z/OS. It is used to identify the server through the administrative console
and scripting. It is a mixed case name and greater than 8 characters in length.
- The "Server short name" is the platform-specific native alias and the
principal name by which the server is known to z/OS. It is used to identify
the server to underlying z/OS facilities, such as the Security Server, JES,
WLM and ARM. For example, the server short name is used as the MVS JOBNAME.
- The "Cluster short name" is used as the WLM application environment name.
A cluster is a logical grouping of like-configured
servers. Clusters exist to promote scalability and availability; workload
balancing occurs across the servers in a cluster. Clusters allow you to partition
workloads into separate servers while still referring to them as a single
unit. Clustering is typically applied to a multinode cell, where each node
is configured on a separate system and the cluster has a member (server) on
each node. Client requests are distributed among the cluster members based
on workload manager decisions.
Note: If you intend for your cluster to span
multiple systems in a sysplex, you might need to set up a shared HFS. See
"Considerations for clustered servers and stateful session beans" for a list
of conditions that would make a shared HFS necessary.
A node
contains servers which may be part of a cluster. The cluster may span nodes
as long as all involved nodes are in the same cell.
Here is a quick
breakdown of clusters, nodes and cells:
- cluster
- A logical collection of like-configured servers. A cluster can span nodes
and systems within the same cell.
- node
- A logical collection of managed servers on a particular system in the
cell. A node can contain servers that are part of clusters that span other
nodes, but the node itself is confined to a single system and a single cell.
You may configure multiple nodes on the same system--either in the same cell
or in different cells. Nodes exist mainly for the purposes of administration,
and each Application Server node managed by a deployment manager must have
a node agent.
- cell
- A logical collection of nodes and the boundary of the administrative domain.
The nodes that comprise a cell must be configured on systems in the same sysplex.
You may configure multiple cells in the same sysplex. Different cells may
have nodes on the same systems, though a given node can be a member of only
one cell. The cell is the largest unit of organization.
To help you understand the interaction between servers,
clusters, nodes and cells, here is a diagram depicting various configurations
you can set up in your Network Deployment sysplex:

Cells
1 and 3 in the illustration depict Network Deployment configuration cells.
Cell 2 is a base configuration cell.