WAS Important interview questions Part-1

1. What is websphere?

The moment you ask this question, the first question that comes to mind is WebSphere applicaiton server. In reality, WebSphere is the name of a product family. IBM has many more products under the brand name WebSphere. WebSphere Application Server , WebSphere MQ, WebSphere Message broker, WebSphere business modeler, WebSphere process Server, WebSphere business monitor, WebSphere integration developer, WebSphere partner gateway are some of the products under this brand name.

2. Whats is a profile in websphere Application Server?

When you install WebSphere application server, executable files and configurations files are seperated. This allows you install the product once and create multiple sets of configurations which uses the same underlying core executables of the websphere application server installation. These are the profiles in websphere application server. As you know, there are many types of profiles and you can create multiple profiles.

3. What does nodeagent do in websphere Application Server?

We will have one nodeagnet per one node. The node agent acts as an mediator between the Deployment manmager and the node.

4. What is Sync in websphere Application Server?

WebSphere application server stores all the configuration data in one central location knows as 'Master repository'. And every node/server will have the local configuration repository. The sycn process make sure that the configuration in both local and master repositories are same and in-sync. The sync is a one dimentional process means, it will sync the configurations only from Master repository ==> local repository.

5. What is websphere plug-in for web server and where do i need to install the plug-in?

It is common practise to have web and app servers on different machines. WebSphere provides a plug-in which enables web server to talk to application server, this is known as web server plug-in. Web server plug-in will have a configuration file named plugin-config.xml which will have referenes to all the servers, clusters, applications, virtual hosts of the websphere application server. You can generate this configuration file from administration console, servers -->web servers. Select a web server and click generate plugin configuration file and then propagate the plugin. This plug-in needs to be installed on the web server machine

6. I don't have WebSphere installed on my web server how do i add to the websphere administration console ?

If you like to add your web server to that WebSphere administration console, you can do that by creating a unmanaged node and then add from servers-->web servers

7. Do i need a web server if i have a websphere application server?

Web Server and WebSphere application server provide two different functionalities. WebSphere application server do has an inbuilt web server functionality but it is recomended to use a seperate web server for many reasons. Some of them are: 1. By seperating web and application server activities, your application serving environment is more secure. 2. Using the webserver you can loadbalance the requests between multiple application servers.

8. How do edit/modify the property/configuration files?

It is recomended to modify all the configurations using the administration console. When you need to make any configuration changes, you need do the apply changes and sync them. Any changes you do at local repository level are discarded upon the next restart of that server because the sync is always from DMGR to local repository and changes are not saved to master repository. For example, if you edit a configuration file of server1 and restart it... the changes are lost. When the server starts it syncs the configuration from master repository.

9. What happens if my DMGR is not running?

DMGR is the single point of failure in WebSphere network deployment model. Even if DMGR is down, rest of the server will contine to run and serve the applications. However, anychanges you make in this situation are not saved to master configuration repository.

10. I installed a new application, what do i need to do before i can access it from the web server URL?

When you install a new application or update an application, your web server need to be aware of the changes. Which means you need to update the web server plug-in configuration file. So after a successful installation of an application with mapping to web server, you need to regenerate the plug-in configuration file and propagate it to web server.

11. what is a connecting pool ?
a connection pool is a cache of database connections maintained so that the connections can be reused when future requests to the database are required. Connection pools are used to enhance the performance of executing commands on a database. In connection pooling, after a connection is created, it is placed in the pool and it is used over again so that a new connection does not have to be established. If all the connections are being used, a new connection is made and is added to the pool. Connection pooling also cuts down on the amount of time a user must wait to establish a connection to the database.

12. What is virtual host in websphere application server?
Virutal host is a configuration not a physical one.  A configuration that lets a single machine resemble multiple host machines. Each virtual host has a logical name and a list of one or more DNS host aliases by which it is known.  By deafult, we wull have a default_house and admin_host virtual hosts defined in websphere application server.

13. how do i connect my application to talk to a database?
To achive this , you need to create a JDBC provider and datasource. The JDBC provider object encapsulates the specific JDBC driver implementation class for access to the specific vendor database of your environment. The data source object supplies your application with connections for accessing the database. The best way to learn more about this task is, login to administration console -->guided activities --> connecting to a database.

14. How can i make sure that my servers are available while restarting a cluster?
Use the option ripplestart ... It first stops and then restarts each member of the cluster.

15. I've made some changes to my applicaiton's web.xml , how and where should i update this file?
You can do this from the administration console. Go to enterprise applications -->select your application and click update. on the next panel, you'll have option to update the entire application, a single module or even a single file or multiple files.
Select the single file option and specify the file's path you like to update . Specify a relative path to the file that starts from the root of the war/ear file. So it looks something like this : app1.war/WEB-INF/web.xml

16. How do i minimize the downtime while i'm updating the applications ?
Use rollout update option. This option sequentially updates an application on multiple cluster members across a cluster. After you update an application's files or configuration, click Rollout Update to install the application's updated files or configuration on all cluster members of a cluster on which the application is installed.
Rollout update will save the application configurations then stops the cluster members on a node then syncs the configuration and stat the clusters members on that node. Then it proceeds to the next node and does the same steps.

17. We are getting a 'class not found' and developers like to know, if that class is being loaded or not. how can i assist them troubleshoot the issue?
WebSphere administration console has an utility using which you can see what classes are loaded at what scope for an application. Go to Troubleshooting -->class loader viewer and select the module.

18. We have some issue with our application server and we tried killing it using kill-9 command, the process disappeared for few seconds but it is back again. We did not start the server but it started. What would be the reason?
Servers > Application Servers > server_name. Then, under Server Infrastructure, click Java and Process Management > Process Definition > process > Monitoring Policy. Here we have an option Automatic Restart, this Specifies whether the process should restart automatically if it fails. On distributed systems, the default is to restart the process automatically.

19. Is there a way i can start my server along with nodeagent ?
Servers > Application Servers > server_name. Then, under Server Infrastructure, click Java and Process Management > Process Definition > process > Monitoring Policy. Here we have an option Node Restart State which specifies the desired behavior of the servers after the node completely shuts down and restarts.
    STOPPED - node agent does not start the server.
    RUNNING - the node agent always starts the server.
    PREVIOUS - the node agent starts the server only if the server was running when the node agent