Weblogic Server Tutorial for Beginners

1. Question: What is the Purpose of Clustering?

Answer: Clustering can be considered the most important unsupervised learning problem; so, as every other problem of this kind, it deals with finding a structure in a collection of unlabeled data.

A loose definition of clustering could be “the process of organizing objects into groups whose members are similar in some way”.

A cluster is, therefore, a collection of objects which are “similar” between them and are “dissimilar” to the objects belonging to other clusters.

So, the goal of clustering is to determine the intrinsic grouping in a set of unlabeled data. But how to decide what constitutes a good clustering? It can be shown that there is no absolute “best” criterion which would be independent of the final aim of the clustering. Consequently, it is the user who must supply this criterion, in such a way that the result of the clustering will suit their needs.

For instance, we could be interested in finding representatives for homogeneous groups (data reduction), in finding “natural clusters” and describe their unknown properties (“natural” data types), in finding useful and suitable groupings (“useful” data classes) or in finding unusual data objects (outlier detection).

2. Question: What is a Durable Subscriber?

Answer: There is an option in the publish/subscribe model for subscribers to receive the messages that were published on the topic when they were disconnected or inactive. This is known as a durable subscription. When the subscriber is inactive, messages are persisted and delivered when the subscriber becomes active. Thus, the durable subscription allows subscribers to disconnect, re-connect again and fetch all the messages published on the topic when they were disconnected.

3. Question: What is a JMS Connection Factory?

Answer: A connection factory is an object that a JMS client (a Java™ program that uses the JMS API) uses to create a connection with a JMS provider (a messaging provider such as WebSphere MQ). You can use WebSphere MQ Explorer to create connection factories and to define the connection parameters that the connection factory will use to create connections.
Connection factories, like destinations, are administered objects and are stored in a JNDI namespace, which is a defined location within the naming and directory service. The initial context defines the root of the JNDI namespace. In WebSphere MQ Explorer, all connection factories are stored in Connection Factories folders in the appropriate context and subcontexts, as shown in the following figure.

In the figure, the connection factory called Connection Factory 1 is stored in the Connection Factories folder of the initial context called File System Initial Context.

When you define a connection factory, you select the messaging provider that is used as the JMS provider (for example, WebSphere MQ or Real-time); a connection factory can create connections only to that messaging provider. For the JMS client to create connections to a different messaging provider, you must create a new connection factory and specify the messaging provider. 

4. Question: What is a License File?

Answer: A License File is a specially formatted ASCII text file that contains encrypted product passcodes for each product you are licensed to run. Each product passcode identifies the number of keys available for that product. The license manager grants or denies access to a product depending on the availability of the license keys associated with each product. 
The following figure presents a sample License File. Each INCREMENT line identifies a product, the number of keys available for the product, and other information. (The INCREMENT lines in your License File might not include every element shown in the example.) The backslash (\) character indicates that the line continues onto the next line.
The lines that begin with a pound sign (#) are comments. The MathWorks Installer uses the information in these comment lines (license server host ID or Internet address) when it processes the License File during installation.

5. Question: What is a Local Transaction?

Answer: This group allows multiple activities to be part of a local transaction. A local transaction group ensures that all participants of the transaction either complete or are rolled back together. However, the local transaction is not equivalent to a XA transaction and does not use a transaction coordinator. Instead single resource performs all its transaction work.

6. Question: What is a Machine?

Answer: Machine design is an important part of engineering applications, but what is a machine? The machine is the device that comprises of the stationary parts and moving parts combined together to generate, transform or utilize the mechanical energy. All the machines are made up of elements or parts and units. Each element is a separate part of the machine and it may have to be designed separately and in assembly. Each element, in turn, can be a complete part or made up of several small pieces that are joined together by riveting, welding, etc. Several machine parts are assembled together to form what we call a complete machine. 

7. Question: What is a Messaging Bridge?

Answer: A Messaging Bridge is a relatively trivial endpoint that simply connects two Message Channels or Channel Adapters. For example, you may want to connect a PollableChannel to a SubscribableChannel so that the subscribing endpoints do not have to worry about any polling configuration. Instead, the Messaging Bridge provides the polling configuration.

By providing an intermediary poller between two channels, a Messaging Bridge can be used to throttle inbound Messages. The poller’s trigger will determine the rate at which messages arrive on the second channel, and the poller’s “maxMessagesPerPoll” property will enforce a limit on the throughput. 

Another valid use for a Messaging Bridge is to connect two different systems. In such a scenario, Spring Integration’s role would be limited to making the connection between these systems and managing a poller if necessary. It is probably more common to have at least a Transformer between the two systems to translate between their formats, and in that case, the channels would be provided as the ‘input-channel’ and ‘output-channel’ of a Transformer endpoint. If data format translation is not required, the Messaging Bridge may indeed be sufficient. 

8. Question: What is a Remote JMS Provider?

Answer: A remote JMS provider is a JMS server that is hosted outside a local stand-alone WebLogic server or outside WebLogic server cluster. The remote JMS server may be a WebLogic or a non-WebLogic (foreign) JMS server.

9. Question: What is the Bootup Process?

Answer: The boot process of a modern system involves multiple phases. Here we will discuss each step, how it contributes to the boot process, what can go wrong and things you can do to diagnose problems during booting. 

Learning the details of the boot process will give you a strong understanding of how to troubleshoot issues that occur during boot – either at the hardware level or at the operating system level.

You should read this document first, and then power on a computer. Note each of the phases described in this section. Some of them will last many seconds, others will fly by very quickly! 
The following components are involved in the boot process.

They are each executed in this order:

  • Power Supply Unit
  • BIOS and CMOS
  • POST tests
  • Reading the Partition Table
  • The Bootloader
  • The Kernel and the Ramdisk
  • OS Kernel and Init
  • Runlevels
  • Getty

10. Question: What is a Stage Deployment?

Answer: The final stage of the New Product Development Process, the Deployment or Launch stage, includes the remaining steps required for the full general release of the product. This stage includes ramp up to volume production, marketing and launch plan implementation, distribution and support.

11. Question: What is Multicast and Unicast in Weblogic?

Answer:

Multicast: Multicast is easier to explain over the Unicast. Multicast is a broadcast UDP option for sending a packet/announcement over to a group that is listening on a specific multicast address and port over which the announcement is sent. There is a defined range for valid Multicast address (224.0.0.1 to 239.255.255.255). Everyone listening to the given address hears the announcement just like following a Twitter post. Some limitations with Multicast is the TTL (time to live) across machines/subnets/routers needs to be adjusted and the routers configured to re-transmit the multicast packet across subnets. 

Unicast: Unicast is more of a point to point UDP option to send the packet to a specific member and not everyone. That way, unicast is more of a private conversation between two individuals while multicast is more of as out to a group or room. Both are UDP based, so there can be losses, unlike TCP that handles re-transmissions on message loss. But Unicast can span across routers and does not have to worry about TTL without everyone hearing the announcement. So, Network Admins, in general, prefer to go with Unicast over Multicast for these reasons.

12. Question: What is Connection Pool?

Answer: 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. Opening and maintaining a database connection for each user especially requests made to a dynamic database-driven website application is costly and wastes resources. In connection pooling, after a connection is created, it is placed in the pool and it is used 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.

13. Question: What is Memory Leak?

Answer: A memory leak is the gradual loss of available computer memory when a program (an application or part of the operating system) repeatedly fails to return memory that it has obtained for temporary use. As a result, the available memory for that application or that part of the operating system becomes exhausted and the program can no longer function. For a program that is frequently opened or called or that runs continuously, even a very small memory leak can eventually cause the program or the system to terminate. A memory leak is the result of a program bug.
Some operating systems provide memory leak detection so that a problem can be detected before an application or the operating system crashes. Some program development tools also provide automatic “housekeeping” for the developer. It is always the best programming practice to return memory and any temporary file to the operating system after the program no longer needs it.

14. Question: What is the Admin Server?

Answer: Admin Server is the central domain configuration interface that is used to create, delete and configure the resources of a domain like managed server, machine, cluster, data source, work managers, etc.

15. Question: What is Node Manager?

Answer: The Managed Servers in a production WebLogic Server environment are often distributed across multiple machines and geographic locations.
Node Manager is a Java utility that runs as a separate process from WebLogic Server and allows you to perform common operations tasks for a Managed Server, regardless of its location with respect to its Administration Server. While the use of Node Manager is optional, it provides valuable benefits if your WebLogic Server environment hosts applications with high availability requirements.
If you run Node Manager on a machine that hosts Managed Servers, you can start and stop the Managed Servers remotely using the Administration Console or from the command line. Node Manager can also automatically restart a Managed Server after an unexpected failure. 

The following sections provide an overview of Node Manager.

Node Manager Environment
Node Manager Capabilities
Node Manager Communications for Lifecycle Operations
To configure and use Node Manager, see Configuring, Starting, and Stopping Node Manager. 

16. Question: What is Silent Mode?

Answer: Silent mode means the interface only listens to the CAN bus. This means the unit does not even provide an ACK frame when a message is placed on the CAN bus correctly. 

The silent mode of Norton Anti-Virus temporarily stops background processes and suppresses notifications or security alerts. The anti-virus software will still protect your computer from malware while it is in silent mode, but you won’t receive any popups, and the software won’t conduct any background scans.

17. Question: What is Graphics Mode?

Answer: Graphics mode is a computer display mode that generates an image using pixels. Today, most users operate their computers in a graphics mode as opposed to a text mode or command-line environment.

Graphics mode A way of displaying images on a computer screen or other graphics devices such that the basic unit is the pixel. Lines and characters on the screen are drawn pixel by pixel. The resolution and complexity of the image depending on how many pixels there are in total, and how many bits are assigned to each pixel. The more bits per pixel, the more different colors or shades of gray. A single graphics device can operate in a number of different graphics modes with different resolutions and color selections. A common mode for a desktop PC would be 1024 by 768 pixels with 256 different colors – chosen from a much larger number – available for each pixel. See also text mode, computer graphics.

18. Question: What is Console Mode?

Answer: Associated with each console input buffer is a set of input modes that affects input operations. Similarly, each console screen buffer has a set of output modes that affect output operations. The input modes can be divided into two groups: those that affect the high-level input functions and those that affect the low-level input functions. The output modes only affect applications that use the high-level output functions. 

The GetConsoleMode function reports the current input mode of a console’s input buffer or the current output mode of a screen buffer. The SetConsoleMode function sets the current mode of either a console input buffer or a screen buffer. If a console has multiple screen buffers, the output modes of each can be different. An application can change I/O modes at any time. For more information about the console modes that affect high-level and low-level I/O operations, see High-Level Console Modes and Low-Level Console Modes. 

The GetConsoleDisplayMode function reports whether the current console is in full-screen mode and whether it communicates directly with the hardware.

19. Question: What is the Managed Server?

Answer: If you run a significant portion of your business operations o­nline, you probably already know of the hassle of finding the right hosting service. Did you know that the problem can be mitigated by purchasing a managed server? A managed server is your own dedicated hosting service that also provides data storage services. In addition, managed servers have their own maintenance and backup systems.

It is important not to confuse managed servers with dedicated shared servers. Shared servers o­nly lease out a part of their memory space to host the clients’ websites or websites. Managed servers are solely for their clients; they can use as much of the space as they please. A managed server affords the client the maximum amount of resources for the best allocation of their time and energy. 

Needless to say, managed servers are o­nly best for medium to large businesses. If you o­nly have a small personal website, you probably do not need a managed server unless you are very worried about possible down-time. This is not a baseless concern, but unless you take your personal website and turn it into a business, you will be better off sticking to a smaller hosting service.

The o­ne big advantage of managed servers is that they relieve the clients of having to maintain the servers themselves. As a matter of fact, the company that owns the server basically rents it out to clients, usually o­n a monthly basis. The company programs the server at the client’s request makes any changes and keeps it physically secure. 

There are some disadvantages to managed servers, however. The largest disadvantage is the cost. Managed servers cost much more than ordinary hosting accounts. Companies want to recoup the costs of running multiple servers at o­nce, and the most typical method is to charge high prices.

20. Question: What is the Administration Server?

Answer: Administration Server is a WebLogic Server instance that maintains configuration data for a domain. You can deploy your application on administration Server but it is recommended to create managed Server and deploy your application in managed server and leave Administration domain for configuration and maintenance.

21. Question: What is a WebLogic Server Cluster?

Answer: A WebLogic Server cluster consists of multiple WebLogic Server server instances running simultaneously and working together to provide increased scalability and reliability. A cluster appears to clients to be a single WebLogic Server instance. The server instances that constitute a cluster can run on the same machine, or be located on different machines. You can increase a cluster’s capacity by adding additional server instances to the cluster on an existing machine, or you can add machines to the cluster to host the incremental server instances. Each server instance in a cluster must run the same version of WebLogic Server.

22. Question: What is a Transaction?

Answer: A transaction is an agreement between a buyer and a seller to exchange goods, services or financial instruments. In accounting, the events that affect the finances of a business must be recorded on the books, and an accounting transaction will be recorded differently if the company uses accrual accounting rather than cash accounting. Accrual accounting records transactions when revenues or expenses are realized or incurred, while cash accounting records transactions when the business actually spends or receives money.

23. Question: What is i3?

Answer: Developed and manufactured by Intel, the Core i3 is a dual-core computer processor, available for use in both desktop and laptop computers. It is one of three types of processors in the “i” series (also called the Intel Core family of processors). 
The Core i3 processor is available in multiple speeds, ranging from 1.30 GHz up to 3.50 GHz, and features either 3MB or 4MB of the cache. It utilizes either the LGA 1150 or LGA 1155 socket on a motherboard.

The most common type of RAM used with a Core i3 processor is DDR3 1333 or DDR3 1600. 

Power usage varies for the Core i3 processors:

Slower speeds (1.30 GHz to 1.80 GHz) use 11.5 W, 15 W or 25 W of power
Medium speeds (2.00 GHz to 2.50 GHz) use 28 W, 35 W or 37 W of power
Faster speeds (2.90 GHz to 3.50 GHz) use 35 W, 37 W or 54 W of power

Core i3 processors are often used in laptop computers, due to their lower heat generation and conservative battery usage. Some laptops can be used for up to five or six hours on a single battery charge when running a Core i3 processor.

24. Question: What is JNDI?

Answer: The Java Naming and Directory Interface™ (JNDI) is an application programming interface (API) that provides naming and directory functionality to applications written using the Java™ programming language. It is defined to be independent of any specific directory service implementation. Thus a variety of directories -new, emerging, and already deployed can be accessed in a common way. 

25. Question: What is Multicast?

Answer: Multicast is a packet or a message sent across a network by a single host to multiple clients or devices.

Multicast is communication between a single sender and multiple receivers on a network. Typical uses include the updating of mobile personnel from a home office and the periodic issuance of online newsletters. Together with anycast and unicast, multicast is one of the packet types in the Internet Protocol Version 6 (IPv6).

Multicast is supported through wireless data networks as part of the Cellular Digital Packet Data (CDPD) technology. 

Multicast is also used for programming on the MBone,a system that allows users at high-bandwidth points on the Internet to receive live video and sound programming. In addition to using a specific high-bandwidth subset of the Internet, Mbone multicast also uses a protocol that allows signals to be encapsulated as TCP/IP packet when passing through parts of the Internet that can not handle the multicast protocol directly.

26. Question: What is Unicast?

Answer: Unicast is communication between a single sender and a single receiver over a network. The term exists in contradistinction to multicast, communication between a single sender and multiple receivers, and anycast, communication between any sender and the nearest of a group of receivers in a network. An earlier term, point-to-point communication, is similar in meaning to unicast. The new Internet Protocol version 6 (IPv6) supports unicast as well as anycast and multicast. 

Unicast is the term used to describe communication where a piece of information is sent from one point to another point. In this case, there is just one sender, and one receiver.

Unicast transmission, in which a packet is sent from a single source to a specified destination, is still the predominant form of transmission on LANs and within the Internet. All LANs (e.g. Ethernet) and IP networks support the unicast transfer mode, and most users are familiar with the standard unicast applications (e.g. https, SMTP, FTP, and telnet) which employ the TCP transport protocol.

27. Question: What is the Server?

Answer: In a technical sense, a server is an instance of a computer program that accepts and responds to requests made by another program, known as a client. Less formally, any device that runs server software could be considered a server as well. Servers are used to manage network resources. For example, a user may set up a server to control access to a network, send/receive an e-mail, manage print jobs, or host a website. 

Some servers are committed to a specific task, often referred to as dedicated. As a result, there are several dedicated server categories, like print servers, file servers, network servers, and database servers. However, many servers today are shared servers which can take on the responsibility of e-mail, DNS, FTP, and even multiple websites in the case of a web server. 

Because they are commonly used to deliver services that are required constantly, most servers are never turned off. Consequently, when servers fail, they can cause the network users and company many problems. To alleviate these issues, servers are commonly high-end computers setup to be fault-tolerant.

Examples of servers:

There are many classifications of servers. Below is a list of the most common types of servers.

  • Application server
  • Blade server
  • Cloud server
  • Database server
  • Dedicated server
  • File server
  • Print server
  • Proxy server
  • Standalone server
  • Webserver

28. Question: What is the Protocol That Will Work When You Use XA Transaction Enabled For JDBC Connections?

Answer: A protocol is a set of rules and guidelines for communicating data. Rules are defined for each step and process during communication between two or more computers. Networks have to follow these rules to successfully transmit data.

A common use of JMS is to consume messages from a queue or topic, process them using a database or EJB, then acknowledge/commit the message.

If you are using more than one resource; e.g. reading a JMS message and writing to a database, you really should use XA – its purpose is to provide atomic transactions for multiple transactional resources.For example, there is a small window from when you complete updating the database and your changes are committed up to the point at which you commit/acknowledge the message; if there is a network/hardware/process failure inside that window, the message will be redelivered and you may end up processing duplicates. 

The problem with XA is it can be a bit slow; as the XA protocol requires multiple syncs to disk to ensure it can always recover properly under every possible failure scenario. This adds significant cost (in terms of latency, performance, resources, and complexity). Also, quite a few EJB servers and databases don’t properly support XA!

29. Question: Why Do You Need ThreadPool How It Works?

Answer: The size of a thread pool is the number of threads kept in reserve for executing tasks. It is usually a tunable parameter of the application, adjusted to optimize program performance. (Why Do You Need ThreadPool How It Works)

The primary benefit of a thread pool over creating a new thread for each task is that thread creation and destruction overhead is restricted to the initial creation of the pool, which may result in better performance and better system stability. Creating and destroying a thread and its associated resources is an expensive process in terms of time. An excessive number of threads in reserve, however, wastes memory, and context-switching between the runnable threads invoke performance penalties. A socket connection to another network host, which might take many CPU cycles to drop and re-establish, can be maintained more efficiently by associating it with a thread that lives throughout more than one network transaction.

Typically, a thread pool executes on a single computer. However, thread pools are conceptually related to server farms in which a master process, which might be a thread pool itself, distributes tasks to worker processes on different computers, in order to increase the overall throughput. Embarrassingly parallel problems are highly amenable to this approach. 

The number of threads may be dynamically adjusted during the lifetime of an application based on the number of waiting tasks. For example, a web server can add threads if numerous web page requests come in and can remove threads when those requests taper down. The cost of having a larger thread pool is increased resource usage. The algorithm used to determine when to create or destroy threads affects the overall performance:

  • Creating too many threads wastes resources and costs time creating the unused threads.
  • Destroying too many threads requires more time later when creating them again.
  • Creating threads too slowly might result in poor client performance (long wait times).
  • Destroying threads too slowly may starve other processes of resources.

30. Question: What is the Non-Profitable Organization That Gives Benchmarking For Each standardization?

Answer: According to the Minnesota State Office of Management & Budget, “benchmarking is simply the comparison of one organization’s practices and performances against those of others. It seeks to identify standards, or ‘best practices’, to apply in measuring and improving performance.” 

Benchmarking is an important part of the nonprofit performance measurement process because it allows your organization to determine where you are starting from. In order to track improvement, it is necessary to establish a baseline, which benchmarking provides. 

This practice also enables your organization to determine standards or best practices that are already part of your processes. This information can be useful as your organization moves on to the next step.

31. Question: If SSL is Configured Then Which Key is Send to the Client?

Answer: CSR KEY (If SSL is Configured Then Which Key is Send to the Client)

32. Question: How Can You Find Out How Many Files Are Opened in Unix Box?

Answer: While administrating a box, you may want to find out what a process is doing and find out how many file descriptors (FD) are being used. You will be surprised to find out that process does open all sort of files:

=> Actual log file

=> /dev files

=> UNIX Sockets

=> Network sockets

=> Library files /lib /lib64

=> Executables and other programs etc

In this quick post, I will explain how to count how many file descriptors are currently in use on your Linux server system.

33. Question: How Can You Get the Deployment Files From Another Box and From Where You Will Get?

Answer: This topic explains how to deploy a Web application project by using one-click publish and the Web Deploy publish method. One-click publish with the Web Deploy publish method enables you to automate most tasks that are required in order to deploy a Web application. (How Can You Get the Deployment Files From Another Box and From Where You Will Get)

To use these features, Web Deploy must be installed on your development computer and the same version of Web Deploy must be installed on the destination Web server. (By default, Web Deploy is installed on the development computer when you install Visual Studio.) If you are deploying to a third-party hosting company, the company must support the version of ASP.NET that your Web application targets and must support one-click publish. For information about how to use one-click publish with other publish methods, see How to: Deploy a Web Application Project Using One-Click Publish Without Web Deploy.

Deploying a Web application project using one-click publish might involve the following additional tasks that are not described in this procedure:

  • Specifying database deployment options. If the Web project that you want to deploy uses a database, and if scripts must run during deployment in order to set up database structures or data in the destination environment, you must enter settings in the Package/Publish SQL tab of the project Properties page. For more information, see How to: Deploy a Database With a Web Application Project.
  • Specifying Web.config file transformations. Web.config files typically include settings that have to be different depending on which environment the application is running in. For example, the Web.config file on your development computer might enable debugging, but you typically do not want debugging enabled for an application that runs on a production server. You can create transform files that automate the process of changing Web.config settings during deployment. For more information, see How to: Transform Web.config When Deploying a Web Application Project

34. Question: Tell Me the Errors u r Getting in the Browser Like 500 How Many Errors Are There Explain?

Answer: Moving over to the server-side error codes, the 500 error is the catchall. When none of the other 500 error codes make sense, or if the programmer is just lazy and doesn’t identify the specific problem, a 500 status code is returned. Typically, you can retry the request attempt again and possibly get a different response. Of course, retrying attempts that involved a shopping cart that resulted in a 500 error could result in a duplicate order, so tread carefully there. 

Basically there are four types of errors in PHP, which are as follows:

  • Parse Error (Syntax Error)
  • Fatal Error
  • Warning Error
  • Notice Error

35. Question: How Can the Cluster Members Will Communicate?

Answer: WebLogic Server instances in a cluster communicate with one another using two basic network technologies:

  • IP sockets, which are the conduits for peer-to-peer communication between clustered server instances.
  • IP unicast or multicast, which server instances use to broadcast the availability of services and heartbeats that indicate continued availability.

Note: When creating a new cluster, it is recommended that you use unicast for messaging within a cluster. For backward compatibility with previous versions, WebLogic Server you must use multicast for communications between clusters. 

The way in which WebLogic Server uses IP multicast or unicast and socket communication affects the way you configure your cluster.

36. Question: How Can You Provide the Security in LDAP Server?

Answer: LDAP is often used by organizations as a central repository for user information and as an authentication service. It can also be used to store the role information for application users. 

There are many different scenarios for how an LDAP server may be configured so Spring Security’s LDAP provider is fully configurable. It uses separate strategy interfaces for authentication and role retrieval and provides default implementations which can be configured to handle a wide range of situations.

You should be familiar with LDAP before trying to use it with Spring Security. The following link provides a good introduction to the concepts involved and a guide to setting up a directory using the free LDAP server OpenLDAP: https://www.zytrax.com/books/ldap/. Some familiarity with the JNDI APIs used to access LDAP from Java may also be useful. We don’t use any third-party LDAP libraries (Mozilla, LDAP, etc.) in the LDAP provider, but extensive use is made of Spring LDAP, so some familiarity with that project may be useful if you plan on adding your own customizations. 

When using LDAP authentication, it is important to ensure that you configure LDAP connection pooling properly. If you are unfamiliar with how to do this, you can refer to the Java LDAP documentation.

LDAP authentication in Spring Security can be roughly divided into the following stages.

  1. Obtaining the unique LDAP “Distinguished Name”, or DN, from the login name. This will often mean performing a search in the directory unless the exact mapping of usernames to DNS is known in advance. So a user might enter the name “joe” when logging in, but the actual name used to authenticate to LDAP will be the full DN, such as uid=joe,ou=users,dc=springsource,dc=com.
  2. Authenticating the user, either by “binding” as that user or by performing a remote “compare” operation of the user’s password against the password attribute in the directory entry for the DN.
  3. Loading the list of authorities for the user.

The exception is when the LDAP directory is just being used to retrieve user information and authenticate against it locally. This may not be possible as directories are often set up with limited read access for attributes such as user passwords.

We will look at some configuration scenarios below. For full information on available configuration options, please consult

37. Question: Tell Me the Errors u r Getting in the Browser Like 500 How Many Errors Are There Explain?

Answer: Moving over to the server-side error codes, the 500 error is the catchall. When none of the other 500 error codes make sense, or if the programmer is just lazy and doesn’t identify the specific problem, a 500 status code is returned. Typically, you can         retry the request attempt again and possibly get a different response. (Company) Of course, retrying attempts that involved a shopping cart that resulted in a 500 error could result in a duplicate order, so tread carefully there.

PHP, which are as follows:

  • Parse Error (Syntax Error)
  • Fatal Error
  • Warning Error
  • Notice Error

38. Question: What are the Steps to Perform For Server Migration?

Answer: 1. Windows ” Server 2003 Microsoft will end support for Windows Server 2003 on July 14, 2015. Companies face a challenge on how to migrate old applications that are no longer supported and should modernize their versions of Exchange, SharePoint, Lync and SQL Server. T» ‘ The number of respondents in the ‘ Spiceworks network of IT professionals that report at least one instance of Windows Server 2003 running in their organization. Haw: an’-. —» ‘1 : :‘c: i;»: . F: fvillvxmw ~1|I. I_i*‘I_n; I W’Iri«*1I~w: .~. :x= Ii‘Y, ‘=Ii’ r~’ri’i; |i*: i?. ’I«nr: : 1. Catalog your software o o – u o – – . . Tools such as Dell’s Enterprise Reporter, ChangeBASE and ChangeAuditor can help companies catalog and analyze applications and workloads according to criticality, complexity and risk. (What are the Steps to Perform For Server Migration)

2. Perform security assessments Security patches for Windows Server 2003 will no longer be available after July 2015. To maintain compliance with regulations such as HIPAA, upgrade to Windows Server 2012.

3. I Identify your destinations Use software such as Dell’s Migration Manager to choose a migration destination for applications and workloads based on speed, ease of migration, cost and functionality.

4. Test all applications Be sure to test all applications in Windows Server 2012 to make sure they run properly in a 64-bit environment before rolling out officially throughout the organization. Software such as ChangeBASE lets companies test application compatibility.

5. Complete the migration Windows ‘ Server 2012 When you’re ready to make the move, reporting tools like Enterprise Reporter can provide analysis before and after a migration. With support for Microsoft’s M SQL Server 2005 database Ali, II _ I management software A ending in 2016, companies could upgrade SQL Server at the same time as Windows Server to avoid a second migration a year later.

39. Question: Which Protocol is Used For the Unicast Clustering?

Answer: The WebLogic Server unicast protocol uses standard TCP/IP sockets to send messages between cluster members. Since all modern networks—and network devices—support TCP/IP sockets, this makes unicast a great out of the box experience for WLS clusters since it typically requires no additional configuration, regardless of the network topology between the cluster members. As a result, WebLogic Server changed the default clustering protocol from multicast to unicast in WLS 10.0.

Unicast is just another cluster message protocol; Oracle fully supports both the unicast and multicast protocols. As stated previously, parts of the WLS documentation suggest or imply that multicast is only supported for backward compatibility. This suggestion or implication is incorrect. The A-team is working with WLS product management to correct this in the WebLogic Server 12c documentation. The choice of protocols should not be influenced by this wording in the WLS documentation. This article tries to provide a balanced view of the two different protocols and makes recommendations on how to choose a cluster messaging protocol for a particular environment.

Since TCP/IP sockets are a point-to-point mechanism, WebLogic Server’s unicast implementation uses a group leader strategy to limit the growth in the number of sockets required as the cluster size grows. The cluster is split into one or more groups; each group has a group leader. Group members communicate with the group leader; group leaders also communicate with other group leaders in the cluster. If a group leader dies, the group elects another group leader.

For small clusters of 10 managed servers or less, the cluster contains a single group and therefore, a single group leader. The other servers in the group make a TCP/IP socket connection to the group leader that they use to send and receive cluster messages. When the group leader receives a cluster message from one server, it retransmits that message to all other members of the group. The group leader acts as a message relay to propagate the messages across the cluster.

For larger clusters, the cluster splits into multiple groups of 10 managed servers. For example, a cluster of 16 managed servers will have two groups, one with 10 members and one with 6. In these clusters with multiple groups, the group leaders are connected directly to one another. When a group leader receives a cluster message, it not only retransmits that message to other members of its group but also to every other group leader. This allows the entire cluster to receive every cluster message. 

When using unicast, the cluster heartbeat mechanism will remove a server from the cluster if it misses a single heartbeat message since TCP/IP is a reliable protocol. Unicast will check every 15 seconds to see if it has missed a heartbeat. This extra 5 second is to allows sufficient time for the message to travel up to 3 hops, from the remote group’s member to the remote group’s leader to the local group’s leader, and finally to the local group’s member. Since the default heartbeat frequency is one heartbeat every 10 seconds, this means it should take no more than 15 seconds to detect that a server has left the cluster. Of course, socket death detection or failed connection attempts can also accelerate this detection. 

40. Question: Which Protocol is Used For Multicast Communication?

Answer: Multicast is the term used to describe communication where a piece of information is sent from one or more points to a set of other points. In this case, there is maybe one or more senders, and the information is distributed to a set of receivers (there may be no receivers or any other number of receivers). (Which Protocol is Used For the Multicast Communication)

One example of an application that may use multicast is a video server sending out networked TV channels. Simultaneous delivery of high-quality video to each of a large number of delivery platforms will exhaust the capability of even a high bandwidth network with a powerful video clip server. This poses a major salability issue for applications that required sustained high bandwidth. One way to significantly ease scaling to larger groups of clients is to employ multicast networking. 

Multicasting is the networking technique of delivering the same packet simultaneously to a group of clients. IP multicast provides dynamic many-to-many connectivity between a set of senders (at least 1) and a group of receivers. The format of IP multicast packets is identical to that of unicast packets and is distinguished only by the use of a special class of destination address (class D IPv4 address) which denotes a specific multicast group. Since TCP supports only the unicast mode, multicast applications must use the UDP transport protocol.

Unlike broadcast transmission (which is used on some local area networks), multicast clients receive a stream of packets only if they have previously elected to do so (by joining the specific multicast group address). Membership of a group is dynamic and controlled by the receivers (in turn informed by the local client applications). The routers in a multicast network learn which sub-networks have active clients for each multicast group and attempt to minimize the transmission of packets across parts of the network for which there are no active clients. 

The multicast mode is useful if a group of clients requires a common set of data at the same time, or when the clients are able to receive and store (cache) common data until needed. Where there is a common need for the same data required by a group of clients, multicast transmission may provide significant bandwidth savings (up to 1/N of the bandwidth compared to N separate unicast clients).

The majority of installed LANs (e.g. Ethernet) are able to support the multicast transmission mode. Shared LANs (using hubs/repeaters) inherently support multicast, since all packets reach all network interface cards connected to the LAN. The earliest LAN network interface cards had no specific support for multicast and introduced a big performance penalty by forcing the adaptor to receive all packets (promiscuous mode) and perform software filtering to remove all unwanted packets. Most modern network interface cards implement a set of multicast filters, relieving the host of the burden of performing excessive software filtering. 

41. Question: What You Will Do When Data Source Will Down?

Answer: To shut down a data source, you can use the Shutdown and Force Shutdown options on the JDBC Data Source: Control page in the Administration Console (see “Shut down JDBC data sources”) or the shutdown() and force shutdown() methods in the JDBCDataSourceRuntimeMBean. 

When you shut down a data source (not forcibly shut down), WebLogic Server closes database connections in the data source and shuts down the data source. If any connections from the data source are currently in use, the operation will fail.

When you forcibly shut down a data source, WebLogic Server closes database connections in the data source and shuts down the data source. All current connection users are forcibly disconnected. 

42. Question: What is Thread Dump When We Collect the Thread Dump?

Answer: A thread dump is a snapshot of the state of all threads that are part of the process. The state of each thread is presented with a so-called stack trace, which shows the contents of a thread’s stack. Some of the threads belong to the Java application you are running, while others are JVM internal threads.

A thread dump reveals information about an application’s thread activity that can help you diagnose problems and better optimize application and JVM performance; for example, thread dumps automatically show the occurrence of a deadlock. Deadlocks bring some or all of an application to a complete halt.

Here now we will see a very common scenario when we find that the JVM process is talking a lot of time in processing the request. Many times we see that the JVM process is stuck/slow or completely Hung. In such a scenario in order to investigate the root cause of the slowness we need to collect the thread dumps of the JVM process which will tell us about the various activities those threads are actually performing. Sometimes some threads are involved in some very high CPU intensive operations which also might cause slowness in getting the response. So We should collect the thread dump as well as the CPU data using the “top” command. Few things to consider while collecting the thread dumps:

1. Collect the thread dump when we see the issue (slowness, stuck/ hung scenario …etc)…

2. Mostly a single thread dump is not very useful. So whenever we collect the thread dump then we should collect at least 5-6 thread dumps. In some intervals like collect 5-6 thread dumps in 10 seconds interval. Like that we will get around 5-6 thread dumps in 1 minute.

3. If we are also investigating that few threads might be consuming high CPU cycles then in order to find the APIs that are actually consuming the high CPU we must collect the Thread dump as well as the “top” command output data almost at the same time. 

43. Question: If the Application is Not Working How Can You TroubleShoot?

Answer: Please use these general troubleshooting steps if you are having any issues when using the Optimum App on Laptop:

1. Reboot your laptop.

2. Attempt to reboot your cable modem by following the steps in the order below:

  • Unplug the power from your modem. Note: If you are using a battery backup, you’ll also need to disconnect the battery from the modem.
  • Unplug the power from your router.
  • Plug the modem back in and wait until it has fully restarted. This can take up to a few minutes. Note: If you are using a battery backup, reconnect the battery to the modem.
  • Plug the router back in and wait 30 seconds.
  • Check your connection between the wireless router and the modem or the modem and our network and attempt to connect to your home network again.

3. Please ensure that you are using the correct connectivity location or Network Name for your wireless network, following the steps below:

Windows 8 / 7 / Vista / XP:

  • Right-click on the Wireless Network Connection icon in the system tray, (lower right-hand corner of your screen).
  • Select Status.
  • Verify that you are connected to your home wireless network.

Mac:

  • Click the Apply button (top-left corner of the screen).
  • Open System Preferences and select Network.
  • Verify that you are connected to your home wireless network

4. If you have followed the steps above and are still having issues with the application, refer to the Uninstall/Reinstall FAQ for instructions on uninstalling and re-installing the Optimum App on Laptop application.

5. If you are still having technical issues when using the Optimum App on Laptop, please contact your local customer service representative.

44. Question: What are the Frequently Used Commands UNIX Commands?

Answer: The UNIX operating system has for many years formed the backbone of the Internet, especially for large servers and most major university campuses. However, a free version of UNIX called Linux has been making significant gains against Macintosh and the Microsoft Windows 95/98/NT environments, so often associated with personal computers. Developed by a number of volunteers on the Internet such as the Linux group and the GNU project, much of the open-source software is copyrighted, but available for free. This is especially valuable for those in educational environments where budgets are often limited. 

UNIX commands can often be grouped together to make even more powerful commands with capabilities known as I/O redirection (for getting input from file input and for outputting to a file) and piping using | to feed the output of one command as input to the next. Please investigate manuals in the lab for more examples than the few offered here.

45. Question: How to Configure the Cluster?

Answer: Before you set up a configuration cluster in the Configuration Cluster interface, log in as a root-level user on the server that you wish to use as the master server. You must also log in as a root-level user on the master server in order to make any configuration changes that you want to copy to the configuration cluster’s servers. 

46. Question: How to Find Out Which Version of the Operating System Install in Server?

Answer: Black magic. Just kidding. When you visit a site with your web browser it sends a little nugget of information to that site called a “User-Agent”. The user agent has a few minor pieces of information about your browser, platform, and OS version. Using this information a guess can be made about what Operating System your using.

Why is it a guess? The user agent your browser sends to the website can be changed very easily. It’s not to be trusted in any way, shape, or form as the truth, but most people generally use browsers who are user agents that have not been changed.

Why is it only generally? Sometimes the people that provide your internet access will modify this user agent so the website can not tell what your browser is or will set the user agent to a general browser type so the site will render the same for everyone. This is not the norm so don’t fret too much.

47. Question: How Do You Check Updated Log File?

Answer: This will give you a scrolling view of the logfile. As new lines are added to the end, they will show up on your console screen. 

For Ruby on Rails, for instance, you can view the development logfile by running the command from your project directory:

tail -f log/development.log

As with all Linux apps, Ctrl+C will stop it. 

48. Question: What Should Be Running From the DB Side to Connect to the Database?

Answer: Once Amazon RDS provisions your DB instance, you can use any standard SQL client application to connect to the instance. In this example, you connect to a DB instance running the Oracle database engine using the Oracle command-line tools. For more information on using Oracle, go to the Oracle website.

Note: This example uses the Oracle sqlplus command-line utility. This utility is part of the Oracle software distribution. To download a stand-alone version of this utility, go to the SQL Plus User’s Guide and Reference. 

49. Question: How to Test the Connection Pool From Console?

Answer: You can manually test individual instances of a data source. When you test a data source, WebLogic Server reserves a connection from the data source, tests it using the standard testing query or the query specified in Test Table Name, and then returns the database connection to the pool of connections. Test results are displayed at the top of the page in the Administration Console.

The manual connection test relies on the Test Reserved Connections and Test Table Name attributes of the data source. Those attributes are set by default. However, if you changed either attribute, the changes will affect the database connection test.

To test a JDBC data source:

1. If you have not already configured testing options for the data source, see Configure testing options for a JDBC data source and configure options for Test Reserved Connections and Test Table Name.

2. In the Domain Structure tree, expand Services, then select Data Sources.

3. On the Summary of Data Sources page, click the data source name.

4. Select the Monitoring: Testing tab.

5. On the Testing page, select the instance of the data source that you want to test.

Date source instances are listed by the server on which they are deployed.

6. Click the Test Table Name button. Test results are displayed at the top of the page.

50. Question: What is the Process For Connecting to the Database From the Application?

Answer: In computer science, a database connection is the means by which a database server and its client software communicate with each other. The term is used whether or not the client and the server are on different machines.

The client uses a database connection to send commands to and receive replies from the server. A database is stored as a file or a set of files on magnetic disk or tape, optical disk, or some other secondary storage device. The information in these files may be broken down into records, each of which consists of one or more fields.

Fields are the basic units of data storage, and each field typically contains information pertaining to one aspect or attribute of the entity described by the database. Records are also organized into tables that include information about relationships between its various fields. Although the database is applied loosely to any collection of information in computer files, a database in the strict sense provides cross-referencing capabilities.

Connections are a key concept in data-centric programming. Since some DBMSs require considerable time to connect, connection pooling is used to improve performance. No command can be performed against a database without an “open and available” connection to it.

Connections are built by supplying an underlying driver or provider with a connection string, which is used to address a specific database or server and to provide instance and user authentication credentials.

Once a connection has been built, it can be opened and closed at will, and properties (such as the command time-out length, or transaction, if one exists) can be set. The connection string consists of a set of key-value pairs, dictated by the data access interface of the data provider. 

Some databases, such as PostgreSQL, only allow one operation to be performed at a time on each connection.[citation needed] If a request for data (a SQL Select statement) is sent to the database and a result set is returned, the connection is open but not available for other operations until the client finishes consuming the result set.

Other databases, such as SQL Server 2005 (and later), do not impose this limitation. However, databases that allow multiple concurrent operations on each connection usually incur far more overhead than those that only allow one operation at a time.

the security namespace schema

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