Network Configuration Files in Oracle

Oracle uses three files (tnsnames.ora, listener.ora and sqlnet.ora) for network configuration. These are explained below:

1. tnsnames.ora file in oracle

TNS stands for Transparent Network Substrate. The "tnsnames.ora" file contains client side network configuration parameters. tnsnames.ora files contains the information which is used by the system to connect to oracle database.

Location of tnsnames.ora in oracle: By default, tnsnames.ora is located in the $ORACLE_HOME/network/admin directory on UNIX operating systems and in the ORACLE_HOME\network\admin directory on Windows operating systems.

Format / Syntax of tnsnames.ora:

net_service_name=
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = yourHostIPAddress)(PORT = portNumber))
    )
    (CONNECT_DATA =
      (SID = databaseName)
    )
  )

Explanation: Syntax contains:

PROTOCOL: Here TCP is used.
HOST IP ADDRESS: Where oracle is installed
PORTNO: Port number of server where oracle is installed
SID: SID stands for System Identifier. SID is the name of database.

Failover and Load-Balancing in tnsnames.ora

Consider the following example

net_service_name=
 (DESCRIPTION=
  (ADDRESS_LIST=
   (LOAD_BALANCE=on)
   (FAILOVER=off)
   (ADDRESS=(PROTOCOL = TCP)(HOST = yourHostIPAddress1)(PORT = portNumber1))
   (ADDRESS=(PROTOCOL = TCP)(HOST = yourHostIPAddress2)(PORT = portNumber2)))
  (ADDRESS_LIST=
   (LOAD_BALANCE=off)
   (FAILOVER=on)
   (ADDRESS=(PROTOCOL = TCP)(HOST = yourHostIPAddress3)(PORT = portNumber3))
   (ADDRESS=(PROTOCOL = TCP)(HOST = yourHostIPAddress4)(PORT = portNumber4)))
  (CONNECT_DATA=
   (SID = databaseName)))

In the above example, we specify the list of addresses which will take over another address in case of failure or overload.

Note: Typically you could have two tnsnames.ora files in the system, one that is set for the entire system and is called the system tnsnames.ora file, and a second file that is used by each user locally so that he can override the definitions dictated by the system tnsnames.ora file.

tnsping: tnsping is used to ping the tnsnames.ora file. If there is no error in tsnnames.ora, it will ping it otherwise error will be displayed.

Format of tnsping command: tsnping hostIPAddress

2. listener.ora file in oracle

The listerner.ora file contains server side network configuration parameters. It is found in the $ORACLE_HOME/network/admin" directory on the server.

Example:

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS_LIST =
        (ADDRESS = (PROTOCOL = TCP)(HOST = hostname)(PORT = port))
      )
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = databaseName.WORLD)
      (ORACLE_HOME = /u01/app/oracle/product/9.2.0)
      (SID_NAME = databaseName)
    )
  )

After the "listener.ora" file is amended the listener should be restarted or reloaded to allow the new configuation to take effect.

C:> lsnrctl help
C:> lsnrctl status
C:> lsnrctl stop
C:> lsnrctl start
C:> lsnrctl reload

3. sqlnet.ora file in oracle: The "sqlnet.ora" file contains client side network configuration parameters. It is present in the "$ORACLE_HOME/network/admin" It contains following settings:

SQLNET.AUTHENTICATION_SERVICES= (NTS)

Above setting is necessary on Windows if OS authentication is required.

NAMES.DIRECTORY_PATH= (TNSNAMES, ,ONAMES, HOSTNAME)

A list of naming adaptors to be used when resolving a name. These will be used in the order listed. TNSNAMES = tnsnames.ora file, ONAMES = Oracle Names, HOSTNAME = use the hostname

40 Objective Type ASP.NET Interview Questions (Part 1)

1. How do you retrieve username in case of Windows Authentication?

System.Environment.UserName

2. What is the control for which by default post back is true?

Button

3. Where the private assembly is stored in asp.net?.

application / bin directory

4. Where the public assembly is stored in asp.net?.

Global Assembly Cache (GAC)

5. What events will occur when a page is loaded?

1) Page_PreInit
2) Page_Init
3) Page_InitComplete
4) Page_PreLoad

6. Where is the View state data stored?

Hidden Fields

7. What are the different types of sessions in ASP.NET?

InProc, StateServer, SQL Server

8. How do you design a website with multilingual support in ASP.NET?

By using Globalization and Localization

9. What are the different ways of caching in ASP.NET?

There are three ways of caching in ASP.NET:

1) Output Caching - Caches the whole page.
2) Fragment Caching - Caches a part of the page
3) Data Caching - Caches the data

10. How Automatic Memory Management is done is ASP.NET?

By using Garbage Collector

11. How many web.config files can be there in an ASP.NET application?

Atleast one

12. How many navigation controls are there in ASP.NET 4.0?

There are three navigation controls in ASP.NET 4.0:

1) SiteMapPath
2) Menu
3) TreeView

13. List various event which occur throughout the life cycle of a page.

1)Page_PreInit
2)Page_Init
3)Page_InitComplete
4)Page_PreLoad
5)Page_Load
6)Control Events
7)Page_LoadComplete
8)Page_PreRender
9)SaveViewState
10)Page_Render
11)Page_Unload

14. What is boxing and unboxing?

Boxing is what happens when a value-type variable is assigned to a reference-type variable.
Unboxing is what happens when a reference-type variable is assigned to a value-type variable.

15. What are the uses of Reflection?

Reflection is a concept using which we can

1) Load assemblies dynamically
2) Invoke methods at runtime
3) Retriving type information at runtime.

16. What is the lifespan for items stored in ViewState?

The items stored in ViewState live until the lifetime of the current page expires.

17. How can we identify that the Page is Post Back?

By using "IsPostBack" property.

18. In which event of page life cycle are the controls fully loaded?

Page load

19. What is the basic difference between ASP and ASP.NET?

ASP is interpreted whereas ASP.NET is compiled

20. Which is the parent class of the Web server control?

The System.Web.Ul.Control

21. How information about the user's locale can be accessed?

Using System.Web.UI.Page.Culture property

22. How do you sign out from forms authentication?

Using FormsAuthentication.Signout() method

23. What is AutoPostBack?

If you want a control to postback automatically when an event is raised, you need to set the AutoPostBack property of the control to True.

24. Define a Multilingual Website.

A multilingual Web site serves content in a number of languages. It contains multiple copies for its content and other resources, such as date and time, in different languages.

25. What is actually returned from server to the browser when a browser requests an .aspx file and the file is displayed?

When a browser requests an .aspx file then the server returns a RESPONSE, which is rendered into a HTML string.

26. How can you display all validation messages in one control?

The ValidationSummary control displays all validation messages in one control.

27. Which two new properties are added in ASP.NET 4.0 Page class?

The two new properties added in the Page class are MetaKeyword and MetaDescription.

28. How can you register a custom server control to a Web page?

You can register a custom server control to a Web page using the @Register directive.

29. Which ASP.NET objects encapsulate the state of the client and the browser?

The Session object encapsulates the state of the client and browser.

30. Which method is used to force all the validation controls to run?

The Page.Validate() method is used to force all the validation controls to run and to perform validation.

31. Which method has been introduced in ASP.NET 4.0 to redirect a page permanently?

The RedirectPermanent() method added in ASP.NET 4.0 to redirect a page permanently.

32. How can you send an email message from an ASP.NET Web page?

You can use the System.Net.Mail.MailMessage and the System.Net.Mail.SmtpMail classes to send an email in your Web pages. In order to send an email through your mail server, you need to create an object of the SmtpClient class and set the server name, port, and credentials.

33. What is the difference between the Response.Write() and Response.Output.Write() methods?

The Response.Write() method allows you to write the normal output; whereas, the Response.Output.Write() method allows you to write the formatted output.

34. What does the Orientation property do in a Menu control?

Orientation property of the Menu control sets the horizontal or vertical display of a menu on a Web page. By default, the orientation is vertical.

35. Can we validate a DropDownList by RequiredFieldValidator?

Yes, we can validate a DropDownList by RequiredFieldValidator. To perform this validation, we have to set the InitialValue property of RequiredFieldValidator control.

36. What are the various ways of authentication techniques in ASP.NET?

There are three ways of authentication in ASP.NET:

Windows Authentication
Forms Authentication
Passport

37. What is the difference between a HyperLink control and a LinkButton control?

A HyperLink control does not have the Click and Command events; whereas, the LinkButton control has these events, which can be handled in the code-behind file of the Web page.

38. How will your write server-side comments?

<%--This is an example of server-side comments --%>

39. How do you prevent a validation control from validating data at the client end?

You can prohibit a validation control to validate data at the client side by setting the EnableClientScript property to False.

40. What do you mean by a neutral culture?

When you specify a language but do not specify the associated country through a culture, the culture is called as a neutral culture.   

SQL Replay: A new feature of Oracle 11g

SQL Replay is a new feature introduced in Oracle 11g. SQL Replay features is used to capture the commands executed in a database and then replay them elsewhere. You can use the capture and replay features to perform diagnostic operations or to test applications under production conditions.

Steps to create SQL Replay:

Step 1: Creating a Workload Directory

The log file for the SQL workload will be written to a directory on the source server. To specify the physical location for that directory, you must create a directory object within the database.

Use the create directory command:

create directory workload_dir as '/u01/workload'

Step 2: Starting the Capture of Source Database

To start a capture, execute the START_CAPTURE procedure of  DBMS_WORKLOAD_CAPTURE package.

BEGIN
  DBMS_WORKLOAD_CAPTURE.START_CAPTURE
        (name => 'practice_capture',
          dir => 'workload_dir',
     default_action => 'EXCLUDE');
END;
/

Note:
1. The name parameter is the name you assign to the workload capture.
2. dir is the name of the directory object you created to store the workload-capture files.

Stopping the Capture:

If you have not specified a duration, you must stop the capture manually. To stop the capture, execute the FINISH_CAPTURE procedure, as shown here:

BEGIN
  DBMS_WORKLOAD_CAPTURE.FINISH_CAPTURE ();
END;
/

Step 3: Processing the Workload Logs:

Workload Logs are transformed into Replay Files and metadata is created. It can be done by PROCESS_CAPTURE procedure of DBMS_WORKLOAD_REPLAY package.

BEGIN
  DBMS_WORKLOAD_REPLAY.PROCESS_CAPTURE
   (capture_dir => 'workload_dir');
END;
/

The capture_dir variable value must be the name of a directory object within the database that points to the physical directory where the workload logs are stored.

Step 4: Replaying the Workload on Target Database

To start the replay, use the START_REPLAY procedure of DBMS_WORKLOAD_REPLAY package, as shown in the following listing:

BEGIN
  DBMS_WORKLOAD_REPLAY.START_REPLAY ();
END;
/

To stop the replay, use the CANCEL_REPLAY procedure, as shown in the following listing:

BEGIN
  DBMS_WORKLOAD_REPLAY.CANCEL_REPLAY ();
END;
/

Precautions while Replaying SQL

1. Before starting the capture on the source database, you should make sure there are no active transactions within the database. Best practice is to restart the database.

2. For best results during the replay, you should alter / reset the system time on the target system.

3. The target database should run the same version of Oracle as the source system.

4. Target database should be separate from the production database and should be as isolated as possible from the external structures accessed by the production database.
Note: Replay is best suited for uses in which the target system is a testing environment, rather than generating the replay in a testing environment and then executing it in a production database

11 Methods to implement 301 Redirect URLs

Need to 301 Redirect URLs:

1. Retains Search Engine Ranking: 301 redirect is the most efficient and Search Engine Friendly method for webpage redirection. It preserves your search engine rankings and indexing for that particular page.

2. Retains your visitors / traffic: If you move your popular page to which a lot of visitors have already linked, you may lose them if you don't used redirect method. This provides a great way to provide your visitors with the information they were looking for and prevent you from losing your traffic.

Methods to 301 Redirect URLs:

1. HTML Redirect / Meta Refresh

Place the following HTML redirect code between the <HEAD> and </HEAD> tags of your HTML code.

<meta HTTP-EQUIV="REFRESH" content="0; url=http://www.yourdomain.com">

The above HTML redirect code will redirect your visitors to another web page instantly. The content="0; may be changed to the number of seconds you want the browser to wait before redirecting.

2. PHP Redirect

<?
Header( "HTTP/1.1 301 Moved Permanently" );
Header( "Location: http://www.new-url.com" );
?>

3. ASP Redirect

<%@ Language=VBScript %>
<%
Response.Status="301 Moved Permanently"
Response.AddHeader "Location","http://www.new-url.com/"
%>

4. ASP .NET Redirect

<script runat="server">
private void Page_Load(object sender, System.EventArgs e)
{
Response.Status = "301 Moved Permanently";
Response.AddHeader("Location","http://www.new-url.com");
}
</script>

5. JSP Redirect

<%
response.setStatus(301);
response.setHeader( "Location", "http://www.new-url.com/" );
response.setHeader( "Connection", "close" );
%>

6. CGI PERL Redirect

$q = new CGI;
print $q->redirect("http://www.new-url.com/");

7. Ruby on Rails Redirect

def old_action
headers["Status"] = "301 Moved Permanently"
redirect_to "http://www.new-url.com/"
end

8. ColdFusion Redirect

<.cfheader statuscode="301" statustext="Moved permanently">
<.cfheader name="Location" value="http://www.new-url.com">

9. Javascript URL Redirect

<head>
<script type="text/javascript">
window.location.href='http://www.newdomain.com/';
</script>
</head>

10. IIS Redirect

In internet services manager, right click on the file or folder you wish to redirect
Select the radio titled "a redirection to a URL".
Enter the redirection page
Check "The exact url entered above" and the "A permanent redirection for this resource"
Click on 'Apply'

11. Redirect to www using htaccess redirect

Create a .htaccess file with the below code, it will ensure that all requests coming in to domain.com will get redirected to www.domain.com. The .htaccess file needs to be placed in the root directory of your old website (i.e the same directory where your index file is placed)
Options +FollowSymlinks
RewriteEngine on
rewritecond %{http_host} ^domain.com [nc]
rewriterule ^(.*)$ http://www.domain.com/$1 [r=301,nc]

Note: This .htaccess method of redirection works ONLY on Linux servers having the Apache Mod-Rewrite moduled enabled.

Partitioned Tables: Types and Advantages

As the number of rows in your tables grows, the management and performance impacts will increase. Backups will take longer, recoveries will take longer, and queries that span an entire table will take longer. You can mitigate the administrative and performance issues for large tables by separating the rows of a single table into multiple parts.

Advantages of Partitioned Tables

1. The performance of queries against the tables may improve because Oracle may have to search only one partition (one part of the table) instead of the entire table to resolve a query.

2. The table may be easier to manage. Because the partitioned table's data is stored in multiple parts, it may be easier to load and delete data in the partitions than in the large table.

3. Backup and recovery operations may perform better. Because the partitions are smaller than the partitioned table, you may have more options for backing up and recovering the partitions than you would have for a single large table.

Types of Partition

1. Range Partition: Divides the table according to the specified range.

Example: Create a Table EMP

create table EMP (EmpID  VARCHAR2(32) primary key, EmpName  VARCHAR2(100));

Lets make partition of this table:

create table EMP (EmpID  VARCHAR2(32) primary key, EmpName  VARCHAR2(100))

partition by range (EmpName)

(partition PART1 values less than ('K') tablespace PART1_TS,
partition PART2 values less than (MAXVALUE) tablespace PART2_TS);

Explanation: The EMP table will be partitioned based on the values in the EmpName column:

partition by range (EmpName)

For any EmpName values less than ‘K’, the records will be stored in the partition named PART1. The PART1 partition will be stored in the PART1_TS tablespace. Any other EmpName will be stored in the PART2 partition.

Note that in the PART2 partition definition, the range clause is

partition PART2 values less than (MAXVALUE)

You do not need to specify a maximum value for the last partition; the maxvalue keyword tells Oracle to use the partition to store any data that could not be stored in the earlier partitions.

2. Hash Partition: A hash partition determines the physical placement of data by performing a hash function on the values of the partition key. In range partitioning, consecutive values of the partition key are usually stored in the same partition. In hash partitioning, consecutive values of the partition key are not generally stored in the same partition. Hash partitioning distributes a set of records over a greater set of partitions than range partitioning does, potentially decreasing the likelihood for I/O contention.

3. List Partition: In list partitioning, you tell Oracle all the possible values and designate the partitions into which the corresponding rows should be inserted.

4. SubPartitions: You can create subpartitions—that is, partitions of partitions. You can use subpartitions to combine all types of partitions: range partitions, list partitions, and hash partitions. For example, you can use hash partitions in combination with range partitions, creating hash partitions of the range partitions. For very large tables, this composite partitioning may be an effective way of separating the data into manageable and tunable divisions