Oracle Weblogic Interview Questions and Answers Q.How do I provide user credentials for starting a server? Ans: When you create a domain, the Configuration Wizard prompts you to provide the username and password for an initial administrative user. If you create the domain in development mode, the wizard saves the username and encrypted password in a boot identity file. A WebLogic Server instance can refer to a boot identity file during its startup process. If a server instance does not find such a file, it prompts you to enter credentials. If you create a domain in production mode, or if you want to change user credentials in an existing boot identity file, you can create a new boot identity file. Q.Can I start a Managed Server if the Administration Server is unavailable? Ans: By default, if a Managed Server is unable to connect to the specified Administration Server during startup, it can retrieve its configuration by reading a configuration file and other files directly. You cannot change the server's configuration until the Administration Server is available. A Managed Server that starts in this way is running in Managed Server Independence mode. Q.What is the function of T3 in WebLogic Server? Ans: T3 provides a framework for WebLogic Server messages that support for enhancements. These enhancements include abbreviations and features, such as object replacement, that work in the context of WebLogic Server clusters and HTTP and other product tunneling. T3 predates Java Object Serialization and RMI, while closely tracking and leveraging these specifications. T3 is a superset of Java Object. Serialization or RMI; anything you can do in Java Object Serialization and RMI can be done over T3. T3 is mandated between WebLogic Servers and between programmatic clients and a WebLogic Server cluster. HTTP and IIOP are optional protocols that can be used to communicate between other processes and WebLogic Server. It depends on what you want to do. For example, when you want to communicate between a browser and WebLogic Server-use HTTP, or an ORB and WebLogic Server-IIOP. Q.How do you set the classpath? Ans: WebLogic Server installs the following script that you can use to set the classpath that a server requires: WL_HOME\server\bin\setWLSEnv.cmd (on Windows) WL_HOME/server/bin/setWLSEnv.sh (on UNIX) Q.How do stubs work in a WebLogic Server cluster? Ans: Clients that connect to a WebLogic Server cluster and look up a clustered object obtain a replica-aware stub for the object. This stub contains the list of available server instances that host implementations of the object. The stub also contains the load balancing logic for distributing the load among its host servers. What happens when a failure occurs and the stub cannot connect to a WebLogic Server instance? When the failure occurs, the stub removes the failed server instance from its list. If there are no servers left in its list, the stubb uses DNS again to find a running server and obtain a current list of running instances. Also, the stub periodically refreshes its list of available server instances in the cluster; this allows the stub to take advantage of new servers as they are added to the cluster. Q.How does a server know when another server is unavailable? Ans: WebLogic Server uses two mechanisms to determine if a given server instance is unavailable. Each WebLogic Server instance in a cluster uses multicast to broadcast regular "heartbeat" messages that advertise its availability. By monitoring heartbeat messages, server instances in a cluster determine when a server instance has failed. The other server instances will drop a server instance from the cluster, if they do not receive three consecutive heartbeats from that server instance WebLogic Server also monitors socket errors to determine the availability of a server instance. For example, if server instance A has an open socket to server instance B, and the socket unexpectedly closes, server A assumes that server B is offline. Q.How are notifications made when a server is added to a cluster? Ans: The WebLogic Server cluster broadcasts the availability of a new server instance each time a new instance joins the cluster. Cluster-aware stubs also periodically update their list of available server instances. Q.How do clients handle DNS requests to failed servers? Ans: If a server fails and DNS continues to send requests to the unavailable machine, this can waste bandwidth. For a Java client application, this problem occurs only during startup. WebLogic Server caches the DNS entries and removes the unavailable ones, to prevent the client from accessing a failed server twice. Failed servers can be more of a problem for browser-based clients, because they always use DNS. To avoid unnecessary DNS requests with browser-based clients, use a third-party load-balancer such as Resonate, BigIP, Alteon, and LocalDirector. These products mask multiple DNS addresses as a single address. They also provide more sophisticated load-balancing options than round-robin, and they keep track of failed servers to avoid routing unnecessary requests. Q.How many WebLogic Servers can I have on a multi-cpu machine? Ans: There are many possible configurations and each has its own advantages and disadvantages. BEA WebLogic Server has no built-in limit for the number of server instances that can reside in a cluster. Large, multi-processor servers such as Sun Microsystems, Inc. Sun Enterprise 10000, therefore, can host very large clusters or multiple clusters. In most cases, WebLogic Server clusters scale best when deployed with one WebLogic Server instance for every two CPUs. However, as with all capacity planning, you should test the actual deployment with your target web applications to determine the optimal number and distribution of server instances. Q.How can I set deployment order for applications? Ans: WebLogic Server allows you to select the load order for applications. WebLogic Server deploys server-level resources (first JDBC and then JMS) before deploying applications. Applications are deployed in this order: connectors, then EJBs, then Web Applications. If the application is an EAR, the individual components are loaded in the order in which they are declared in the application.xml deployment descriptor. Q.How do I increase WebLogic Server memory? Ans: Increase the allocation of Java heap memory for WebLogic Server. (Set the minimum and the maximum to the same size.) Start WebLogic Server with the -ms32m option to increase the allocation, as in this example: $ java ... -ms32m -mx32m ... This allocates 32 megabytes of Java heap memory to WebLogic Server, which improves performance and allows WebLogic Server to handle more simultaneous connections. You can increase this value if necessary. Q.What is TTL in Weblogic? Ans: The Multicast TTL(TTL-Time to Live) setting specifies the number of routers a multicast message can pass through before the packet can be discarded. To configure the multicast TTL for a cluster, you should change the Multicast TTL value in the WebLogic Server administration console. This sets the number of network hops a multicast message makes before the packet can be discarded. Q.What are the difference between Connection pool and data source? Ans: Connection Pool is physically connects to the Database. where as Data Source is a logical resource that can be used by developer or any other resource for accessing Connection of pools. DataSource can be associated with JNDI name that is used for looku p from any other client. Q.What is HTTP tunneling? How can we configure it on Weblogic? Ans: HTTP tunneling provides a way to simulate a stateful socket connection between WebLogic Server and a Java client when your only option is to use the HTTP protocol. It is generally used to tunnel through an HTTP port in a security firewall. HTTP is a stateless protocol, but WebLogic Server provides tunneling functionality to make the connection appear to be a regular T3Connection. Steps to configure Http tunneling. Login into the Admin Console, click on the server on which you want to enable he Http Tunneling feature Click on the Protocols tab ? General ? check the “Enable Tunneling” check box. Now you can communicate with the JVMs (Server Instances) using protocols other than t3 Q.Explain the use of HTTP ? Ans: HTTP is the protocol that is made used for the purpose of enabling communication between the WebLogic server and processes. Q.Explain the functionality of IIOP ? Ans: IIOP is a kind of protocol helpful in enabling the communication between WebLogic server and object request broker. Q.Explain the term clustering? Ans: Clustering is the process of grouping the servers together for accomplishing high percentage of scalability and availability. Q.What is the purpose of clustering? Ans: The major goal of performing the process of clustering is to make high scalability as well as availability of the servers possible. This process also helps in balancing the load in a proper manner and also accomplishes failover. Q.How can cluster communication occur? Ans: The communication through cluster is made possible by the multicast IP as well as port by the process of sending periodic messages which are normally called as heartbeat messages. Q.What is a Node Manager? Ans: Node manager is a utility or process running on a physical server that enables starting, stopping, suspending or restarting admin and managed server remotely. It is not associated with a domain, though can start any server that reside on same physical server. it is required if we use Admin console to start servers. There is two types of NM,
- Script based.
Q.Can a WebLogic Server (WLS) admin server running on a 32-bit JDK be configured with a managed server running on a 64-bit JDK? Ans: This is not a supported Oracle WebLogic Server configuration. This configuration will cause failures of cluster communication between the 32- and 64-bit JVMs. Oracle WebLogic Server supports only homogeneous domain configurations. It is recommended to have all WLS instances (admin and managed servers) to be on the same JDK level and also the same WLS product version. Q.How can we define in weblogic configuration how many concurrent users are allowed or can be allowed at a time to a particular application? Ans: If to each user you assign a session, then you can control the max number of sessions in your webapp weblogic descriptor, for example adding the following constraint : 12 It's more effective (if you mean 1 user = 1session) than limit ing the number of requests by work managers. Another way, when you can't predict the size of sessions and the number of users, is to adjust memory overloading parameters and set : weblogic.management.configuration.WebAppContainerMBean.OverloadProtectionEnabled. Another way is to define a work manager which will set the limit on number of threads that can access the application which will generally set the limit on number of users. Q.how can we tell how may threads are being used in a weblogic at a time? Ans: Capacity of threads is managed by WebLogic through work managers. By default, just one exists : default with unllimited number of threads (!!!). If we need to exactly find the number of threads being processed by an application ,check the servers/monitoring/Threads tab. Q.What is weblogic Singleton service? Ans: A singleton service is a service running on a managed server that is available on only o ne member of a cluster at a time Q.What is the difference between -Dweblogic and setting values in weblogic console? Ans: When you use -Dweblogic.XXX option you can ovverride console configuration Q.How to disable admin port in weblogic without weblogic console? Ans: edit the config.xml in Domain/Config location find this node and change the value to 'false' true Q.What Is a WebLogic Server Cluster? Ans: A WebLogic Server cluster consists of multiple WebLogic Server server instances running simultaneously and working together to provide increased scalability and reliability. Q.What Are Dynamic Clusters? Ans: Dynamic clusters consist of server instances that can be dynamically scaled up to meet the resource needs of your application. A dynamic cluster uses a single server template to define configuration for a specified number of generated (dynamic) server instances. Q.What Are the Benefits of Clustering? Ans: Scalability The capacity of an application deployed on a WebLogic Server cluster can be increased dynamically to meet demand. You can add server instances to a cluster without interruption of service—the application continues to run without impact to clients and end users. High-Availability In a WebLogic Server cluster, application processing can continue when a server instance fails. You "cluster" application components by deploying them on multiple server instances in the cluster—so, if a server instance on which a component is running fails, another server instance on which that component is deployed can continue application processing. Q.What is a Domain? Ans: A domain is an interrelated set of WebLogic Server resources that are managed as a unit. A domain includes one or more WebLogic Server instances, which can be clustered, non-clustered, or a combination of clustered and non-clustered instances. A domain can include multiple clusters. A domain also contains the application components deployed in the domain, and the resources and services required by those application components and the server instances in the domain Q.What is multicast storm? Ans: If server instances in a cluster do not process incoming messages on a timely basis, increased network traffic, including negative acknowledgement (NAK) messages and heartbeat re-transmissions, can result. The repeated transmission of multicast packets on a network is referred to as a multicast storm Q.How to Find the Weblogic bit version? Ans: Weblogic is coming as a GENERIC distribution. It is a Java program running on top of a VM so there is no need for Weblogic -64bit or Weblogic -32bit versions. On the other hand, the JVM running Weblogic must be either 32bit or 64bit depending on the architecture. Q.Why we need Weblogic Inactive Connection Timeout? Ans: A leaked connection is a connection that was not properly returned to the connection pool in the data source. To automatically recover leaked connections, you can specify a value for Inactive Connection Timeout on the JDBC Data Source. ( Configuration: Connection Pool page in the Administration Console.) When you set a value for Inactive Connection Timeout, WebLogic Server forcibly returns a connection to the data source when there is no activity on a reserved connection for the number of seconds that you specify. When set to 0 (the default value), this feature is turned off. Q.How do I integrate JNI ( Native code ) code into weblogic?' Ans: The LD_LIBRARY_PATH environment variable should be set in the setWLSEnv.sh or the startWLS.sh scripts Q.What is Weblogic Thread Local Safety? Ans: WebLogic does not reset user set ThreadLocal variab les when the thread is returned back to the pool - the user is responsible for managing them. When such threads are reused, its likely they will interfere. You may run into memory leaks since the thread local reference isn't cleaned up. You can safely reset your thread locals prior to returning the thread back to the container. The ThreadLocal.remove() call should clean it up (ensure that its done in a finally block) Q.What is admin Role in weblogic deployment? Ans: The Administration Server for the domain manages the deployment process, communicating with the Managed Servers in the cluster throughout the process. Each Managed Server downloads components to be deployed, and initiates local deployment tasks . The deployment state is maintained in the relevant MBeans for the component being deployed. Q.What is the deployment process in weblogic? Ans: in WebLogic Server, applications are deployed in two phases. Before starting, WebLogic Server determines the availability of the Managed Servers in the cluster.First Phase of Deployment - During the first phase of deployment, application components are distributed to the target server instances, and the planned deployment is validated to ensure that the application components can be successfully deployed. During this phase, user requests to the application being deployed are not allowed. Failures encountered during the distribution and validation process will result in the deployment being aborted on all server instanc es—including those upon which the validation succeeded. Files that have been staged will not be removed; however, container-side changes performed during the preparation will be reverted. Second Phase of Deployment - After the application components have been distributed to targets and validated, they are fully deployed on the target server instances, and the deployed application is made available to clients. When a failure is encountered during the second phase of deployment, the server starts with one of the following behaviors: If a failure occurs while deploying to the target server instances, the server instance will start in ADMIN state. See "ADMIN State" in Managing Server Startup and Shutdown for Oracle WebLogic Server. Q.How do you differentiate between a server hang and server crash issue? Ans: When a Server crashes, the JAVA process no longer exists. When the Server is hung, it stops responding. We can use the weblogic.ADMIN utilty to ping the server. In case of a hang situation we can take multiple thread dumps and analyze the cause of hang. Q.What are deployment descriptors? Ans: It is a configuration file for web application or EJB application which is to be deployed to web or EJB container. Deployment descriptors describes the deployment settings of an application or module or component. It contains meta data describing the contents and structure of the enterprise beans, and runtime transaction and security information for EJB container. It directs a deployment tool to deploy a module or application with specific container options and describes specific configuration requirements that a deployer must resolve. Q.What is a shutdownhook? Ans: A shutdown hook is simply an initialized but unstarted thread. When the virtual machine begins its shutdown sequence it will start all registered shutdown hooks in some unspecified order and let them run concurrently. When all the hooks have finished it will then run all uninvoked finalizers if finalization-on-exit has been enabled. Finally, the virtual machine will halt. Q.What is maxexecutethread? Ans: Execute thread count, at the heart of WebLogic Server, is a pool of java threads (execute threads), which do all the work allowing for the parallel execution of tasks. By default this pool has 15 threads, but can be changed for performance tuning by setting the weblogic.system.executeThreadCount in weblogic.properties. Q.Can a WebLogic Server (WLS) admin server running on a 32-bit JDK be configured with a managed server running on a 64-bit JDK? Ans: This is not a supported Oracle WebLogic Server configuration. This configuration will cause failures of cluster communication between the 32- and 64-bit JVMs.Oracle WebLogic Server supports only homogeneous domain configurations. It is recommended to have all WLS instances (admin and managed servers) to be on the same JDK level and also the same WLS product version. Q.What is the difference between green threads and native threads? Ans: Green threads are the default threads provided by the JDK. Native threads are the threads that are provided by the native OS: Native threads can provide several advantages over the default green threads implementation, depending on your computing situation. Q.How can I increase the number of Posix reader threads? Ans: Modifying the weblogic.system.percentSocketReader is not having any effect on the number of Posix reader threads. In the command line which starts WebLogic for Unix: -Dweblogic.PosixSocketReaders In the command line which starts WebLogic for Windows: -Dweblogic.NTSocketReaders NOTE: PosixSocketReaders relates to the number of Posix reader threads. Q.What is a File Descriptor? Ans: A file descriptor is a handle represented by an unsigned integer used by a process to identify an open file. It is associated with a file object that includes informat ion such as the mode in which the file was opened, its position type, its initial type, and so on. This information is called the context of the file. Weblogic Interview Questions Weblogic Interview Questions and Answers Q.What are the available deployment tools in weblogic? Ans: WLS has several modes to deploy an application:
- from the administration console
- Deployer tool
- wldeploy ant task
- management.deploy API
- by copying the module under applications directory if running in development mode.
Q.What is a deployment unit? Ans: A deployment unit refers to a J2EE applic ation (an Enterprise Application or Web Application) or a standalone J2EE module (an EJB or Resource Adapter) that has been organized according to the J2EE specification and can be deployed to WebLogic Server. WebLogic Server also supports deploying Web Services modules, which are not part of the J2EE specification. Q.What is virtual Hosting? Ans: Virtual hosting, which defines a set of host names to which Oracle WebLogic Server instances (servers) or clusters respond. When you use virtual hosting, you use DNS to specify one or more host names that map to the IP address of a server or cluster. You also specify which Web applications are served by each virtual host. Q.What are security providers? Ans: Security providers, which are modular components that handle specific aspects of security, such as authentication and authorization. Q.What are Resource adapters? Ans: Resource adapters, which are system libraries specific to Enterprise Information Systems (EIS) and provide connectivity to an EIS. Q.What are Persistent Store? Ans: Persistent store, which is a physical repository for storing data, such as persist ent JMS messages. It can be either a JDBC-accessible database or a disk-based file Q.What are Startup classes? Ans: Startup Classes are Java programs that you create to provide custom, system-wide services for your applications. Q.What are work Managers? Ans: Work Managers, which determine how an application prioritizes the execution of its work based on rules you define and by monitoring actual run-time performance. You can create Work Mangers for entire Oracle WebLogic Server domains or for specific application components. Q.What happens when configuration file are deleted? Ans: We can configure Weblogic server to make back up copies of the configuration files. This helps in recovery when configuration needs to be reversed or in case configuration files are corrupted. When the admin server starts up, it saves a JAR file named config-booted.jar that contains the configuration file, the old ones are saved in the configArchive directory under the domain directory, in a jar named like config-1.jar. Q.How does Credentials are passed to Weblogic server? Ans: Credentials to the weblogic server can be passed in multiple ways as
- pass the credentails on the command line
- pass them to the weblogic server when it asks on the command prompt
- Create a boot.properties file and store the user C redentials in an encrypted format
- For WLST scripts that contain commands requiring a user name and password, create a user configuration file. This file, which you can create via the
WLST storeUse rConfig command
- For we blogic.Deployer scripts containing commands requiring a user name and password, you can specify the user configuration file created via the
WLST storeUse rConfig command instead of entering your unencrypted credentials. Q.What is an administration Mode in Production deployment? Ans: Distributing an application copies deployment files to target servers and places the application in a prepared state. You can then start the application in administration mode, which restricts access to the application to a configured administration channel so you can perform final testing without opening the application to external client connections or disrupting connected clients. You can start an application in administration mode with the - adminmode option Q.What are the available roles in weblogic? Ans: The built-in security roles for "Admin" and "Deployer" users allow you to perform deployment tasks using the WebLogic Server Administration Console. The "AppTester" security role allows you to test versions of applications that are deploy ed to administration mode. When deploying across WebLogic domains, the "CrossDomainConnector" role allows you to make inter-domain calls from foreign domains. Admin , View the server configuration, including the encrypted value of some encrypted attributes. Modify the entire server configuration Deploy Enterprise Applications and Web application, EJB, Java EE Connector, and Web Service modules and Start, resume, and stop servers. Operator , View the server configuration, exc ept for encrypted attributes and can Start, resume, and stop servers. Monitor ,View the server configuration, e xc ept for encrypted attributes .This security role effectively provides read-only access to the WebLogic Server Administration Console, WLST, and MBean APIs. Q.What is Denial-of-Service attack? Ans: A Denial-of-Service attack is a malicious attempt to overload a server with phony requests. One common type of attack is to send huge amounts of data in an HTTP POST method. You can set three attributes in Web Logic Server that help prevent this type of attack. These attributes are set in the Console, under Servers or Virtual Hosts Q.Can an application be deployed without any deployment descriptors? Ans: Yes an application can be deployed to J2ee complaint server with out any deployment descriptors by making use of the annotations or the container having reasonable defaults. The exploded archive can also be deployed with out any deployment descriptors Q.What is a fast swap deployment? Ans: fast swap deployment allows to deploy changes to the existing applications in a fast manner. Java EE 5 introduced the ability to redefine a class at run time without dropping its classloader or abandoning existing instances. This allowed containers to reload altered classes without disturbing running applications, vastly speeding up iterative development cycles and improving the overall development and testing experiences. Q.What is OPatch? Ans: OPatch is a Java-based utility that runs on all supported operating systems and requires installation of the Oracle Universal Installer. It is used to apply patches to Oracle software. This is used to patch not just weblogic but the whole Oracle fusion. OPatch offers many of the same features as Smart Update, but it has a different set of commands and command options. Q.What is a weblogic version compatibility? Ans: The version compatibility says that all weblogic servers in a domain must be the same versions of Weblogic version runnings. This means that in WebLogic Server 12.1.3, the Administration Server, Managed Servers, and the WebLogic domain must all be at version 12.1.3. Q.Can weblogic cluster be configured in a mixed platform? Ans: Yes , weblogic cluster can be configured in a mixed platform systems but it can cause negative impact on load balancing and performance. If you must operate a cluster on a mixed platform, Oracle strongly recommends that you understand the load balancing and performance implications. Q.Can a node manager run with a different version of weblogic version? Ans: Oracle recommends that the version of Node Manager used in a WebLogic domain should match the version of the Administration Server. Q.What is a WebLogic Diagnostics Framework? Ans: The WebLogic Diagnostics Framework (WLDF) is a monitoring and diagnostic framework that defines and implements a set of services that run within WebLogic Server processes and participate in the standard server life cycle. Using WLDF, you can create, collect, analyze, archive, and access diagnostic data generated by a running server and the applications deployed within its containers. This data provides insight into the run-time performance of servers and applications and enables you to isolate and diagnose faults when they occur. Q.What is a Harvester in WLDF? Ans: Harvester is used to Captures metrics from run-time MBeans, including WebLogic Server MBeans and custom MBeans, which can be archived and later accessed for viewing historical data Q.What are Watches and Notifications in WLDF? Ans: These Provides the means for monitoring server and application states and sending notifications based on criteria set in the watches. Q.What are the types of data sources provided in weblogic? Ans: There are 3 types of data sources provided in weblogic . they are
- Generic Data Sources—Generic data sources and their connection pools provide connection management processes that help keep your system running efficiently.You can set options in the data source to suit your applications and your environment.
- GridLink Data Sources—An event-based data source that adaptively responds to state changes in an Oracle RAC instance.
- Multi data sources—An abstraction around a group of generic data sources that provides load balancing or failover processing.
Q.What are the types of Session Replication in weblogic ? Ans: Weblogic uses 2 types of Session replication methods, they are in- memory replication - Using in- memory replication, WebLogic Server copies a session state from one server instance to another. The primary server creates a primary session state on the server to which the client first connects, and a secondary replica on another WebLogic Server instance in the cluster. The replica is kept up-to-date so that it may be used if the server that hosts the servlet fails. JDBC-based persistence -In JDBC-based persistence, WebLogic Server maintains the HTTP session state of a servlet or JSP using file-based or JDBC-based persistence Q.Can we create a replica-aware stub? Ans: If you are using EJBs then just define the home-is-clusterable" or "stateless-bean-is-clusterable" in (weblogic -ejb-jar.xml) clusterable to *TRUE* by default those values are true.. Q.Is it possible in Weblogic to create readonly JDBC datasource? Ans: The datasource allows you to obtain pooled connection instances, each pooled connection instance representing a physical connection to a database that remains open during use by a series of logical connection instances. So, what you are allowed to do with a pooled connection instance strictly depends on the database permissions granted to the user used to create the physical connection. In other words, if you want a read only pool, use a user with restricted rights at the database level when creating your pool. Q.How WebLogic Server (10.3.2) initializes its Security Provider Database at startup? Ans: The security provider database should be initialized the first time security providers are used. (That is, before the security realm containing the security providers is set as the default (active) security realm.) This initialization can be done:
- When a WebLogic Server instance boots.
- When a call is made to one of the security provider's MBeans.
Q.What is weblogic sever life cycle? Ans: There are 9 states of server:-
- Shutting down
The series of states through which a WebLogic Server instance can transition is called the server life cycle. Q.What are Locks in weblogic? Ans: There are 4 types of loc k available in weblogic config.lok : This is used for the getting the file lock on the config.xml file.This lock ensures that the config.xml file is being owned by only one process at a time.This also ensures that the updates to config.xml file are done in a sequential order. Location : cfgdir/config/config.xml edit.lok : This was the most important lock that we see.This lock ensures that only one user is editing the configurations at any point of time. No 2 operations are performed at a same time Location : cfgdir/ embeddedLDAP.lok:This file locks access to the embedded ldap server to ensure that only one person has access to the directory server at any time. Location /cfgdir/servers//data/ldap/ldapfiles/ XXXServer.lok:This lock indicates that a given server is running.This ensures that the server is not started or running multiple times. Location : /cfgdir/servers//servername.lok When a webloigc server is stopped, the embeddedLDAP.lok and XXXservername.lok are deleted automatically. Q.How can I set deployment order for applications? Ans: WebLogic Server allows you to select the load order for applications. WebLogic Server deploys server-level resources (first JDBC and then JMS) before deploying applications. Applications are deployed in this order: connectors, then EJBs, then Web Applications. If the application is an EAR, the individual components are loaded in the order in which they are declared in the application.xml deployment descriptor. Q.Can I refresh static components of a deployed application without having to redeploy the entire application? Ans: Yes. You can use weblogic.Deployer to specify a component and target a server, using the following syntax: java weblogic.Deployer -adminurl http://admin:7001 -name appname - targets server1,server2 -deploy jsps/*.jsp Q.How do I turn the auto-deployment feature off? Ans: The auto-deployment feature checks the applications folder every three seconds to determine whether there are any new applications or any changes to existing applications and then dynamically deploys these changes. The auto-deployment feature is enabled for servers that run in development mode. To disable auto-deployment feature, use one of the following methods to place servers in production mode:
- In the Administration Console, click the name of the domain in the left pane, then select the Production Mode checkbox in the right pane.
- At the command line, include the following argument when starting the domain’s Administration Server: -Dweblogic.ProductionModeEnabled=t rue
Production mode is set for all WebLogic Server instances in a given domain. Q.Can I enable requests to a JDBC connection pool for a database connection to wait until a connection is available? Ans: No, there's no way to allow a request to wait for a pool connection, and from the system point of view there should not be. Each requests that waits for a connection ties up one of the fixed number of execute threads in the server, which could otherwise be running another server task. Too many waiting requests could tie up all of the execute threads and freeze the server. Q.How many admin consoles possible in a single domain ? Ans: only one. Q.What is boot.properties file ? Ans: boot.properties is the file used by admin or managed server during startup for username and password. it exist under your domain/servers/server_name/security folder. Q.What are muxer threads? Ans: These are the Special Threads in Web logic Server to read incoming request from external entities on the servers. The main usage is to read the incoming request and then pass them to either “execute Thread” or “work Manager”. Weblogic allocates a percentage of the Thread pool for these pools.The default value is 33% and not more than 50%. Q.what is JRCMD? Ans: There is a tool called “jrc md” provided with JRocket jdk which sends commands to the JRocket jvm. This is a command line tool available in the JRcoket/bin/ Q.What are connection filters? Ans: Connection Filter is another feature provided by weblogic, which is a network layer security. These connection filters allow unwanted access to resources. For example these can be used in blocking a IP address in accessing the admin console of a weblogic Q.What is SNMP? Ans: The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices and it is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. SNMP enables network administrators to manage network performance, solve and find network problems, and plan for network growth. Q.What is a light weight weblogic container? Ans: Normally when a web logic servers is started , the server type is wls . This server type basically starts all types of servers , but when we start the weblogic server with wlx options the server starts in a light weight mode. The "wlx" option starts a server instance that excludes the following services, making for a lighter weight runtime footprint: Enterprise JavaBeans (EJB) Java EE Connecter Architecture (JCA) Java Message Service (JMS) Just pass the “-DserverType=wlx “ to the startWeblogic.sh Script Q.How do you Bind an IP address to a weblogic server? Ans: There are cases where we need to run a web logic server by binding it to a specific IP address. This helps in case when we have multiple web logic server instances running on same machine which has multiple network interfaces. First, you should bind the address as follows: java -msXXm - mxXXm … -Dweblogic.system.bindAddr=xxx.xxx.xxx.xxx weblogic.Server Q.How do clean application Cache in Weblogic? Ans: Application cache is available in the Servers directory that are created when ever we start the Managed Servers. This directory contains one sub directory for each Oracle Web Logic Server instance in the domain. The sub directories contain data that is specific to each server instance. In Order to clean the application Cache , we can go to /servers//t mp/_WL_user/ In this location we will see all applications that were deployed to this server. We can delete the application for which we want to clean the cache. Before doing that please stop the server, delete the application cache and then restart the Server again. Q.How do we Clean the EJB Cache? Ans: For cleaning the EJB Cache just go to /domains/servers//cache/EJBCompilerCache. and remove the EJBCompilerCache and restart the Servers. The EJB files are again recompiled. This will be helpful when dealing with many EJB based applications Q.What is advantage if silent mode installation ? Ans: for this sailent mode of installation you need to specify the log file and xml file. The difference between command and sailent mode is command mode=console i.e here step by step are visible but in sailent mode every thing is configured. The biggest advantage of silent mode installation is that it is non-interactive and hence your intervention is not required during installation. All the parameters to be used during installation are defined in xml file (usually silent.xml) eg:./filename.bin - mode=silent -silent_xml=silent.xml Q.What does 'stub' mean in weblogic server? Ans: clients that connect to a WLS instances and look like a single clustered object obtain a replica-aware-stub of the object. The stub contains the list of all the available server instances of the object .It also has a load balancing logic to distribute the load across the multiple hosts. Q.What is multicast Address? Ans: An address that can be used to send the messages to the same host addresses but in different network addresses.that addresses can be referred as multicast address.The multicast addresses are in the range 220.127.116.11 to 18.104.22.168. Q.What is Garbage collection? Ans: Garbage collection (GC) is a form of automatic memory management. The garbage collector attempts to reclaim garbage, or memory occupied by objects that are no longer in use by the program. Q.What are the different types of WLST modes? Ans: There are Two types of connection modes: 1)Offline Mode: WLST helps you to create and extend a domain, and create domain templates. In offline mode, WLST acts as an interface to the Node Manager and you can issue WLST commands to start and stop Managed Server instances without connecting to the Admin Server. 2)Online Mode: WLST in online mode acts as a Java Management Extensions (JMX) client that manages the domain’s resources by modifying the server’s Configuration MBeans. Thus, WLST offers you all the domain management configuration capabilities as the Administration Console. Q.What are Heap, Core and Thread dumps? Ans: A heap dump is a snapshot of memory at a given point in time. It contains information on the Java objects and classes in memory at the time the snapshot was taken.'' A core dump is the printing or the copying to a more permanent medium (such as a hard disk ) the contents of random access memory ( RAM ) at one moment in time. One can think of it as a full-length "snapshot " of RAM. A core dump is taken mainly for the purpose of debugging a program. A thread dump is a list of all the Java threads that are currently active in a Java Virtual Machine (JVM). Q.How to check the Weblogic Version? Ans: We can use the registery.xml file contact for more on Oracle Weblogic Online Training
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