1 what is a connection 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.
2. What is virtual host in websphere application server?
Virtual 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 default, we wull have a default_house and admin_host virtual hosts defined in websphere application server.
3. 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.
4. 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.
5. 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
6. 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.
7. 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 a 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.
8. 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.
9. 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 stopped.
Note: The questions answered in this series are some of the questions i was asked through email from my blog subscribers/users.
Next FAQ session is a compilation of questions on SSL.