500 Internal Server Errors

Any website or application which is hosted in IIS returns the response status as either success or failure. 501 is the HTTP status code which IIS returns to the user and is recorded in IIS log files. The IIS log files are saved at following folder location: inetpublogsLogfiles.Due to HTTP 500 Internal Server Error, the website cannot display the page. HTTP 501 errors also denotes that the configuration is not implemented. HTTP 501 Error is server side error.

Cause of HTTP 501-Internal Server Error:

 1. If IIS cannot access the configured root directory of the source code folder this error could occur.
2. In source code folder, there might be possible that there are multiple config files exist and some of them are conflicting.
3. ISAPI.dll is a file that can process the request and mapping point to this file are missing.
4. If any handler mappings for the requested resource points to .dll file are missing then they cannot process the request and screen would display as HTTP 501 Internal Server Error.
5. If any new feature is implemented and web server doesn t support that feature, the same error would generates.

Resolution: 1. Go to Start-> Run ->type inetmgr.exe click OK.
2. At IIS Manager, expand server name and Web sites, and then click the Web site.
3. In Features view of IIS window, double-click Handler Mappings.
4. Mapping points to the correct ISAPI.dll file for asp files should map to the below folder locationthe%windir%system32inetsrvasp.dll file).
5. Refresh the web page after clearing the browser s cache and deleting the browser s cookies.
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Some Ways To Improve The SQL Server Performance

There are some of various ways and by adopting them we can inhance the sql server performance . Some of them are as follows :

Improving SQL Query

SQL queries could be written in many ways but a developer should have to use the bet queries to make the performance more better.

Prevent to add multiple function in a single query:

Various function such as email article printing sharing should be avoided to be done by a single query.
This could increase the load of database query and inccur increment in process timing. To avoid such jargon try to use different queries for different purposes. or  to avid this issue the nested loop joins could be used.

Avoid to use Cursors in Query

Just avoid to use cursors in queries because the set based queries are much better. If the cursor is needed in queries then at that situation try to avoid dynamic cursor which limits the use of nesed loop joins by optimizer.

Avoid Multi-statement functions (TVFs)

These inline are less costly than the multi statement functions. The inline TVFs is being expand by server into various main query and also seperate the context
from main query. which makes TVFs very costly.

Include indexes :

Indexed table always reduce the interval timing of data but this also effects on DML operations adversly. This also be decrease theperformance of queries.
Indexing is type of challenge but its a fact that  it improve the perforance of sql queries and also improves the query timing.

Understand the Data

By understanding the data type we can identify the type of queries to be used to retrieve the data. After creating the database when data entered sucessfully and
when indexing be done properly this desicion should be took carefully that what types of queries should be used their to retrieve the data. If their is a need then
mention a unique key which leads the query. To avoid any type of overhead just one should have to choose the coloumn correctly and make appropriate changes.

Include coloumn in index
Include coloumn in indexed table is important because it helps to improve the performance o sql queries. By including coloumn in table helps queries to search
data very easily without searching the whole database due to which the sql query performance improves. When the required content matched with the content of
a coloumn its can be easily retrieved. when the database in not properly indexed or coloumned then it also creates very much difficulties to retrieve the data and
also creates very much overload on sql server.

Delete useless indexes :

Deleting useless indexes decrease the size of database due to which the sql load also decreases and the data retrieval become less time taking. Which just
speed up the sql performance and data modofication. The small size of database also helps to decrease the overhead use of server resources.

Regular Updates :

There must be a regular updation is needed for coloumns as by optimizing the coloumns done by queries. Regualar updates also inhace the quality of queries.

Include som special keys :
By inclusion of some keys such as NOT NULL , FORIGEN KEY, PRIMARY KEY etc also improves the sql sever performance. 
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HTTP Error 502 Bad Gateway

It is an HTTP status code indicating that one server has received some invalid response from another server that it was accessing. This may happen while the receiving server attempts to load a web page or fill another request by the browser. The root cause can be attributed to poor IP communication between the computers at the back-end including the web server at the site one is trying to visit.
Thus, it can be said that it arises due to some network error between servers across the Internet. So, actually the problem is not with some individual PC or Internet connection. However, few things can be done at the PC end, to troubleshoot or resolve the problem.


I. Refresh/ reload the web page or press Ctrl+F5 or type in the URL again on the address bar. Trying this thing often proves successful.

II. Clear cache and temporary Internet files. Also check if the firewall is functioning correctly.

III. Try again later. Since the issue is with the website network, it is fairly possible that everyone visiting the particular site is facing the same problem. So, one can expect that the problem has already been brought to the notice of the administrator and he is working towards resolving it.

IV. Send an e-mail to the administrator or the webmaster. The e-mail id of most of the webmasters is webmaster at the rate website.com, where website.com has to be replaced with the actual website name.

 Including the Web server at the site you are trying to visit. Before analyzing this problem, you should clear your browser cache completely.


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HTTP Error 503 - Service unavailable

This type of error message comes when at any particular point of time, the web server which runs the website is not able to handle the HTTP request or the server does not agree with the socket connection. This arises due to temporary overloading or maintenance of the server. This is a temporary issue that usually gets fixed in a small time interval. This error is reported to return more often in IIS 6.0 as compared to the earlier versions. This error may also occur when the application pool is not started or enabled.

Error cycle:

I. Obtaining IP address of the site.

II. Opening an IP socket connection to that IP address

III Writing an HTTP data stream corresponding to that IP socket

IV Receiving an HTTP data stream from the web server in response

Fixing the error:

I. The web server can be closed temporarily for repair. The client accessing the site can expect that someone is looking after the issue and the usual services will resume soon.

II. The system operators of the website can be contacted. They will be able to help out the client in the best possible way.

III. Refresh/ reload the web page or type in the URL again or press Ctrl+F5.

IV. Restart the router and then the PC, especially if  Service Unavailable – DNS Failure error notification comes.

V. Come back later. It is also possible that many people accessing the site leave and then the page is made available to the new requests.


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Network Gateway

Network Gateways are the most sophisticated internetworking tools that are used for connecting dissimilar networks that use different communication protocols. The networks which are built on completely different communication architectures can be interconnected using gateways. The network which are disconnected by a gateway use different protocols and hence protocol conversion is major job performed by gateways.

A broadband router at home networks, typically serves as network gateway but ordinary computers can also be configured to perform same functions. A Gateway may be used to interconnect two networks one of which uses IP Suite and other uses SNA protocol suite.Gateways are also defined as router or proxy server that that perform routing functions between networks. Gateways are operating at any network layer and hence they are also referred as protocol converters.When an IP address of the node of computer network that network software uses does not match any other routes in routing table a default gateway is used.

The outside network (Internet) and internal networks are connected with gateways.

For any organization in a network, This gateway node of a computer system server may also be used as firewall server or a proxy server.
Network gateway is a type of internetworking which is also had ability to join two different networks along with each other and also both these network also shares different protocols.
A subnet mask defines The IP range of any private network is defined on subnet masks.

Any Client should sent IP packet along with its destined place which is not into the given subnet mask towards a network gateway, with in a particular IP network. Such as If any network had a subnet mask of 266.266.266.0 and its Ip is 192.168.1.72 then in such case the data moving towards this IP address outside to 192.168.1.72 will automatically be sent towards that private network gateway. On the other hand when the IP packet is being forwarded on to the other network, then at this situation the gateway either able to or not able to fulfills the translation of network address.

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TCP/IP

TCP stands for Transmission control protocol and IP stands for Internet Protocol. It is the basic communication language or protocol of Internet. If the communication protocol is used as a private network then the protocol is used in Intranet or Extranet. To ensure reliability, ordered and error-checkeddelivery of data over a logical connection, TCP is used.This protocol is used at Transport Layerof Open System Interconnections (OSI) model.

Application programs send a large chunk of data across the Internet using IP. The software issues a single request to TCP and let TCP handle the IP details, instead of breaking the data into IP-sized pieces and issuing a series of IP requests.
The pieces of information which is exchanged are called packets. A packet is a sequence of bytes(octets) and consists of header followed by a body. The header describes the packets source address, destination address and control information. The body contains the data IP is transmitting.

IP(Internet Protocol) is connectionless protocol where no connection is required between sender and receiver to send any message. The message sending through IP may take adifferent route because each packet of message is transferred independently. This protocol is used at Network Layerof Open System Interconnections (OSI) model. X.25 Protocol is also a network layer protocol but is connection-oriented protocol. It is a lower layer of OSI model and handles the address part of each message packets so that it gets to right destination.In this protocol, a request for connection is first sent to destination. If the connection gets accepted the requesting party is given a connection identifier to use for further subsequent requests

Some of the higher layer Application protocols use TCP/IP to get to the Internet.World Wide Webs Hypertext Transfer Protocol (HTTP), the File Transfer Protocol (FTP), Telnet (Telnet), Simple Mail Transfer Protocol (SMTP), POP3, IMAP, SSH use TCP/IP.
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Types of Networking

When more than one are computers linked together and are used to share any type of information or resources or any files needs to exchange, a telecommunications network or data network is used.  With the help of telephone, radio waves, lines, satellites, etc computers of a network could be connected successfully. The example of best known computer network is Internet. We can send emails, photographs, videos, documents, files etc.

Networks are broadly classified into two categories: LAN (Local Area Network) and WANs (Wide Area Network).

Networks that share some characteristics of both LANs and WANs are referred as MANs(Metropolitan Area Networks).

The hardware device which allows a computer to be connected to network both as physically and functionally is called as NIC (Network Interface Cards) or Network Card. NIC is a printed circuit board and is installed on one of expansion slots of computer and provides a port on back of computer to which the network cable is being attached.

The term Network Topology refers how the nodes (two or more computers) of a network are linked together. The data path that may be used between any pair of nodes in network is also referred by Network Topologies.

Types of Network Topologies

Star Network
Ring Network
Completely Connected Network
Hybrid Network
•Multi Access Bus Network


To install a computer networks a combination of factors are keep in mind

a. Performance of the system.
b. Number of nodes and their geographical distribution (size) of the system.
c. Availability of lines of communication.
d. Expandability of system.
e. Calculating the combined cost of components and services required to establish a network.



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