regd jvms and nodes...

[senthil nathan narayan]

hi,
i have few questions though it may seem to be basic in websphere, but i'm interested to know the details about this in websphere...
1. Is there a limitations in configuring the number of applications in for a single Virtual Host
2. Will Each node run only one Administartive server
3. In an application server how many JVM's are recommended
4. Is there a Stack and Heap size for Websphere..if so when will it come into act because JVM has Heap and Stack size.

[Mahesh Chalil]

1. A virtual host can host as many applications as long as they have different webcontexts.
2. Each Server Process runs one Administrative server.
The Admin service runs within each server JVM. In the base configuration, the Admin service runs in the application server. In the Network Deployment configuration, each of the following servers host an Admin service:
 Deployment Manager
 Node agent
 Application server
 JMS server
The Admin service provides the necessary functions to manipulate configuration data for the server and its components. The configuration is stored in a repository; a set of XML files is stored in the server's file system.

Please read these points too:
You can install the base WebSphere Application Server product more than once on a single machine.
You can also install the base WebSphere Application Server product once and create multiple configuration instances on the machine, using the wsinstance command.
You can also install the Network Deployment product once and create multiple configuration instances of the deployment manager.
Each deployment manager configuration instance can federate stand-alone base WebSphere Application Server product installation instances, but a deployment manager cannot federate base product configuration instances.
Only one system hosts the deployment manager.
Although you can install a base WebSphere Application Server on the same machine as the deployment manager, it is not generally done unless you have a machine with the capacity to host both products.
The deployment manager is the central administrative manager. It does not install the base WebSphere Application Server product on other machines. You must do that separately.
The only functions supported in the Network Deployment installation are the deployment manager and its associated administrative programs.
A multiple node environment places WebSphere Application Server processes on separate physical machines, under the central management of the deployment manager process, which groups application servers into its managed cell.
The deployment manager coordinates all application server processes through node agent processes, each of which runs as the nodeagent server on a node.

[Mahesh Chalil]

On question 3 and 4.
3. An instance of an application server runs in a single Java Virtual Machine (JVM) process. However, the inherent concurrency limitations of a JVM process prevents it from fully utilizing the processing power of a machine. Creating additional JVM processes provides multiple thread pools, each corresponding to the JVM associated with each application server process. This avoids concurrency limitations and enables the machine's processing power to be fully used.
Vertical scaling provides a straightforward mechanism for creating multiple instances of an application server, and hence multiple JVM processes. This enables the application server to make the best possible use of the processing power of the host machine.
4. Yes, there is stack size and heap size in websphere. You can set the same using JVM Parameter settings through Admin console or using command line. Usually these parameters determine the Garbage collection frequency. Read IBM Materials on GC to understand how these configurations affect the same.

[senthil nathan narayan]

Thanks....