we deploy web application to WAS server. If we need to restart the web application deployed on the server, do we have to restart the server ? If so, then all the applications deployed on that server will be restarted, right ? Is it possible to just start one application without restarting the entire WAS server ?
Welcome to the ranch !
No, you don't need to restart WAS to restart a web application. Via admin console, as well as via scripting, you can start and stop any application independently from other applications deployed in the same application server.
There could be rare cases when changes in web application settings will require restart server too (e.g.: JNDI names, etc..), but in general , yes - application can be started / stopped independently from server.
Java Platform, Enterprise Edition 6 Web Services Developer Certified Expert Exam Study Guide and Quiz Exam 1Z0-810: Upgrade to Java SE 8 Programmer Study Guide and Quiz