If you are preparing for a WebLogic interview, we’ve got you covered. Below is a list of the most common questions that interviewers ask during WebLogic interviews. We have also provided a sample answer to each question to help you know the best way to respond and prepare adequately for your next interview.
1. Explain The Server Life Cycle Concept
Server Life Cycle refers to a series of operational states that the WebLogic Server instance transitions in the life cycle management. These operational states result in some particular changes to the state of the server instance. They also help in the identification of accurate status when the server is functioning. System administrators use Server Life Cycle commands to keep track of a booting server with the aim of identifying booting issues that cause server conflict. The ultimate goal is to enhance the scalability of a WebLogic server. The Server Life Cycle includes various components such as state transitions and startup parameters.
2. What Is The Difference Between Shutdown State And Starting State
When a WebLogic server instance is in a shutdown state, it is configured but remains inactive. A WebLogic server assumes a shutdown state after a Shutdown or when forced to shut down through a command. A server can also enter the shutdown state in case it detects that it is unstable. On the other hand, a starting state occurs when a WebLogic server changes from a shutdown state to a standby mode. A server instance transitions from a shutdown state to a starting state following a Start in Standby, Start in Admin or Start command.
3. Describe How A Rmi Subsystem Deals With Work In Progress During Suspending Operations
The Remote Method Invocation (RMI) suspends requests in three steps. During this process, each step ends before the start of the subsequent step. In the first step, non-transition requests that are made remotely are rejected by RMI. In the second step, the transaction service initiated by the client waits until the pending transactions are completed. During the third and last step, all the remote requests, whether with transactions or not, are rejected by the remote RMI service. Once these three steps are done, no other requests from remote clients are allowed.
4. Explain The Difference Between Http And T3 Protocols
HTTP refers to the hypertext transfer protocol that is found within the internet protocol suite. It primarily facilitates Web browsers to communicate data across collaborative and distributed systems on the Web. HTTP is a client-server protocol that allows users to exchange when resources like HTML documents by exchanging hypertext messages between servers and clients. On the other hand, T3 is a protocol that helps WebLogic servers to transport information. Java programs also use T3 to transport information. For a WebLogic server to pass some information to a Java virtual machine, it creates a T3 connection. The T3 protocol also improves efficiency and speed by minimizing packet sizes.
5. What Is The Purpose Of The Boot Identity File
A boot identity file stores the credentials used by WebLogic server users to start and stop an instance. A managed server or an administration server refers to the boot identifying the file for these user credentials rather than prompting to provide them at the command line. The advantage of using the boot identity file is that credentials are encrypted. This means it is more secure than storing unencrypted user credentials in a shutdown or startup script. If a boot identity file does not exist, a server will prompt for a username and password.
6. What Is The Difference Between Multicast And Unicast In Weblogic Servers
Multicast consists of a broadcast UDP option that sends an announcement or packet to a group through a particular multicast port or address. Multicast communications work within a specific address range, meaning that everyone listening must be within the specified address range to hear the announcement. On the contrary, Unicast is a point-to-point UDP option that sends an announcement to a particular member, rather than everyone. Thus, Unicast helps to support private communication between two people while multicast is used to communicate to a group. However, both are based on UDP.
7. What Do You Understand By User Datagram Protocol
User Datagram Protocol (UDP) refers to the communication protocol that helps networked computing devices to exchange messages. UDP subdivides messages into packets known as datagrams. These are forwarded networked devices such as security gateways, routers, and switches to the destination server. UDP includes port numbers in the header of datagrams that help to differentiate various messages as well as various user requests.
8. Explain The Difference Between A Weblogic Admin Server And A Managed Server
An administration server constitutes an instance of a WebLogic server that is responsible for maintaining the configuration data for a domain. It is the central point from where an administrator configures as well as manages and monitors all the resources of a domain. A managed server, however, is a WebLogic server instance running on a Java virtual machine and which has its own configuration. Java components are deployed in a managed server and this server functions independently unless when clustered with other servers.
9. How Do Managed Servers Interact With The Administration Server
An administration server functions as the location where the master copy of the domain configuration is stored. This includes the configuration for every managed server within the domain. Each individual server also contains a file that contains a local copy of the domain configuration. Thus, whenever a managed server starts running, it links to the admin server with the aim of synchronizing the configuration. If the configuration changes, the admin server conveys the new configuration to the managed server or servers.
10. Tell Us Some Weblogic Features Under The Application Architecture
WebLogic server offers important features for deploying and developing applications that are across distributed, computing environments. One of them is flexible Web services. WebLogic provides a robust platform that helps admins to deploy Web services. These services employ cross-language and cross-platform models to achieve interoperability across systems. Rich client options are another feature of WebLogic servers. These servers support Web browsers as well as other HTTP clients. Enterprise e-business scalability, robust administration, e-commerce-ready security, Java Message Service, standards leadership, and maximum deployment and development flexibility are other WebLogic features under the application architecture.
11. What Are The Primary Components Of A Weblogic Server
The WebLogic server has five fundamental components. These are Admin Server, Node Manager, Domains, WebLogic Server Cluster, and Managed Server. These components help a WebLogic server to fulfill its middleware role of developing as well as deploying and running Java and other enterprise applications.
12. Tell Us How You Would Provide User Credentials To Start A Weblogic Server
When creating a domain, a WebLogic server will bring up a configuration wizard that will prompt me to enter a username and a password. At this point, I will enter a username and a strong password for the server. The wizard will then save these credentials in a boot identity file. The WebLogic server instance refers to the boot identity file when starting up. Otherwise, it asks the user to enter a username and password.
13. Is It Possible To Start A Managed Server When The Admin Server Is Not Available?
During startup, a managed server can by default retrieve its configuration whenever it fails to connect to the indicated admin server. If a managed server starts in this manner, it runs in an independent mode. It is worth noting that one cannot change the configuration of the server until the time when the admin server will be available.
14. Explain The Meaning Of A Weblogic Server Cluster
A WebLogic Server cluster constitutes several WebLogic server instances that are working together and running simultaneously to enhance reliability and scalability. To clients, a cluster appears as a single WebLogic Server instance. A WebLogic Server cluster can run on a single machine or multiple machines. The capacity of a cluster can be enhanced by adding more server instances to the machine with a cluster. Alternatively, one can add machines to host the incremental server instances. All server instances within a cluster run the same WebLogic Server version.
15. Tell Us Some Benefits Of Clustering
The first important benefit provided by WebLogic clustering is scalability. This is the ability of an application to increase its capacity dynamically to satisfy demand. The second benefit is load balancing, which consists of the capacity to distribute requests to all members in a cluster based on each server’s workload. The third important benefit is high availability. This consists of a mixture of features that make sure that services and applications are available even when a machine or server fails. High availability enables clients to continue working without disruptions.
16. What Is The Relationship Between A Domain And A Cluster?
A cluster is usually a portion of a specific WebLogic server domain, which is a set of interrelated resources of a WebLogic server that are often managed as a single unit. A single domain constitutes one or multiple server instances that can be non-clustered or clustered. A domain can also contain non-clustered or clustered server instances.
17. Explain The Meaning Of MSI Mode In Weblogic. How Can This Mode Be Enabled?
MSI mode simple means Managed Server Independence mode. A managed server works in an independent mode when the administrator server is not available. In such a case, the managed server instance triggers the MSI mode to start. The Managed Server Independence mode is configured from the Admin Console. To start this mode, one needs to make sure that the root directory of the managed server has the config subdirectory. In case this subdirectory is missing, one needs to copy it from the root directory of the Administration Server. Then, the independent mode can be started using a script or a command line by choosing the name of the specified server and then enabling the MSI mode by ticking the related box.
18. What Mechanisms Do A Weblogic Server Employ To Detect The Unavailability Of Another Server?
WebLogic servers use two main methods to know whether a given server is unavailable. These are the use of “heartbeat” messages and monitoring socket errors. A server can multicast to transmit regular “heartbeat” messages that show its availability. Other servers monitor these messages to determine if a server is still functioning or it has failed. In case one server fails to receive heartbeat messages from another server three consecutive times, it will conclude that the server has failed. WebLogic servers also know when another server has failed by monitoring socket errors. If a server, for instance, had an open socket to another server, and that socket closes abruptly, the assumption is that the concerned served has gone offline.
19. Why Do You Think You Are The Right Candidate For This Position
I have been working with WebLogic servers for the past eight years. Over this period, I have gained significant knowledge and experience in these servers. From configuration and troubleshooting admin and managed servers to monitoring and maintaining these servers, I have the skills and experience you are looking for. I am well-versed in different ways to start and stop WebLogic servers. If hired, I will apply my skills and expertise to perform this role as expected.
20. What Are The Roles Performed By A Weblogic Server Administrator
A WebLogic server admin is responsible for developing procedures and processes associated with the WebLogic server and related utilities. He or she ensures that all systems have the minimum specifications needed to run WebLogic servers. The administrator also monitors these servers to enhance performance and also identify issues that need to be resolved. He or she also installs and configures WebLogic domains, conducts performance tuning as well as develops and oversees procedures to ensure everything runs smoothly according to the set standards.
21. How Does A Typical Day Of A Weblogic Administrator Look Like
WebLogic administrators perform various duties every day that include installing WebLogic patches, service packs, and WebLogic domains. The upgrade systems, troubleshoot logs, conduct maintenance checks, and develop automated scripts. They liaise with vendors regarding application issues, monitor performance of servers and related applications, create SQL queries, deploy Web applications, and manage distributed systems and sessions. They also configure node managers as well as configure and administer clusters.
22. What Qualities Should A Weblogic Server Administrator Possess To Become Successful
To become successful, a WebLogic server administrator should have excellent communication skills to be able to liaise with system administrators, database administrators, and end-users. He or she should be well-organized, hardworking, and be able to meet set deadlines. The WebLogic admin should be a team player, problem solver, have an analytical aptitude, be able to work under pressure, and have strong decision-making skills.
23. What Is JNDI?
JNDI stands for Java Naming and Directory Interface. It is an application programming interface that helps to locate data sources using naming services like the Domain Name System (DNS). A naming service works by linking names with objects as well as identifying objects that will be used. Thus, JNDI provides an interface that acts as a common denominator to naming services. These services keep groups of bindings that associate names with things. JNDI also helps components located within distributed applications to find one another. If a resource is moved from one server to another, all applications that were using the moved resource must be updated. But with JNDI, that is not necessary. It’s only the related resource binding that should be updated and all the applications will still be able to access the moved resource.
24. How Do Subs Operate Within Weblogic Server Cluster During Failure
During a time of failure within the WebLogic server, Stubs operate by removing any instance that has failed. Stubs use the Domain Name System (DNS) to know the running server as well as obtain a list of application instances that are available. The list of available instances is refreshed periodically and thus Stubs have to keep checking to know which instances are available at a given time.
25. Is Weblogic A Web Server Or An Application Server?
WebLogic is an application server with the ability to host both enterprise applications such as Java and Web applications. A WebLogic server supports different services and infrastructure and it has the ability to deploy applications and components through Web Services Description Language (WSDL), Universal Description, Discovery, and Integration (UDDI), etc. WebLogic can provide services to static and dynamic requests generated by JSP and HTML. A WebLogic server helps to deploy and develop distributed and multitier applications. It centralizes application services including business components, Web server functionality as well as offering access to backend enterprise systems.
Our list of WebLogic interview questions and answers will equip you with the knowledge you need to ace your next interview. Study it to know the most common questions and the best ways to respond to them. Customize the answers to fit your particular context and situation. Don’t forget to dress decently and arrive early for the interview.