Database LINK creation in ORACLE

DATABASE LINK CREATION

To create a Database Link between two servers (server1 accessing server2) :
1. First create a user in server2 with necessary Grants(specify according to the operation to be performed on server2)
2. Then open the server1, create a entry(give any name ex:ENTRYNAME) for server2 in tnsnames.ora( with server2
     Ipaddress,SID etc;)

3. Test tnsping for server2 with the entry name given in tnsnames.ora
4. Once test worked, then connect to server1 and give the following command to create public link between the servers
     create public database link EXAMPLE.COM connect to USERNAME identified by <password> using 'ENTRYNAME'(last 
     one,entry name should be in quotes)
5. Now the connection established. Test the access through any sql query in server1
    ex: select count(*) from USERNAME.TABLENAME@EXAMPLE.COM (Here the table located in server2)
    result : gives the count of server2 table

RAILS

Variables are the memory locations which holds any data to be used by any program.

There are five types of variables supported by Ruby. You already have gone through a small description of these variables in previous chapter as well. These five types of variables are explained in this chapter.

Ruby Global Variables:

Global variables begin with $. Uninitialized global variables have the value nil and produce warnings with the -w option.

Assignment to global variables alters global status. It is not recommended to use global variables. They make programs cryptic.

Here is an example showing usage of global variable.

#!/usr/bin/ruby

$global_variable = 10

class Class1

def print_global

puts "Global variable in Class1 is #$global_variable"

end

end

class Class2

def print_global

puts "Global variable in Class2 is #$global_variable"

end

end

class1obj = Class1.new

class1obj.print_global

class2obj = Class2.new

class2obj.print_global

Here $global_variable is a global variable. This will produce following result:

NOTE: In Ruby you CAN access value of any variable or constant by putting a hash (#) character just before that variable or constant.

Global variable in Class1 is 10

Global variable in Class2 is 10

Ruby Instance Variables:

Instance variables begin with @. Uninitialized instance variables have the value nil and produce warnings with the -w option.

Here is an example showing usage of Instance Variables.

#!/usr/bin/ruby

class Customer

def initialize(id, name, addr)

@cust_id=id

@cust_name=name

@cust_addr=addr

end

def display_details()

puts "Customer id #@cust_id"

puts "Customer name #@cust_name"

puts "Customer address #@cust_addr"

end

end

# Create Objects

cust1=Customer.new("1", "John", "Wisdom Apartments, Ludhiya")

cust2=Customer.new("2", "Poul", "New Empire road, Khandala")

# Call Methods

cust1.display_details()

cust2.display_details()

Here @cust_id, @cust_name and @cust_addr are instance variables. This will produce following result:

Customer id 1

Customer name John

Customer address Wisdom Apartments, Ludhiya

Customer id 2

Customer name Poul

Customer address New Empire road, Khandala

Ruby Class Variables:

Class variables begin with @@ and must be initialized before they can be used in method definitions.

Referencing an uninitialized class variable produces an error. Class variables are shared among descendants of the class or module in which the class variables are defined.

Overriding class variables produce warnings with the -w option.

Here is an example showing usage of class variable:

#!/usr/bin/ruby

class Customer

@@no_of_customers=0

def initialize(id, name, addr)

@cust_id=id

@cust_name=name

@cust_addr=addr

end

def display_details()

puts "Customer id #@cust_id"

puts "Customer name #@cust_name"

puts "Customer address #@cust_addr"

end

def total_no_of_customers()

@@no_of_customers += 1

puts "Total number of customers: #@@no_of_customers"

end

end

# Create Objects

cust1=Customer.new("1", "John", "Wisdom Apartments, Ludhiya")

cust2=Customer.new("2", "Poul", "New Empire road, Khandala")

# Call Methods

cust1.total_no_of_customers()

cust2.total_no_of_customers()

Here @@no_of_customers is a class variable. This will produce following result:

Total number of customers: 1

Total number of customers: 2

Ruby Local Variables:

Local variables begin with a lowercase letter or _. The scope of a local variable ranges from class, module, def, or do to the corresponding end or from a block's opening brace to its close brace {}.

When an uninitialized local variable is referenced, it is interpreted as a call to a method that has no arguments.

Assignment to uninitialized local variables also serves as variable declaration. The variables start to exist until the end of the current scope is reached. The lifetime of local variables is determined when Ruby parses the program.

In the above example local variables are id, name and addr.

Ruby Constants:

Constants begin with an uppercase letter. Constants defined within a class or module can be accessed from within that class or module, and those defined outside a class or module can be accessed globally.

Constants may not be defined within methods. Referencing an uninitialized constant produces an error. Making an assignment to a constant that is already initialized produces a warning.

#!/usr/bin/ruby

class Example

VAR1 = 100

VAR2 = 200

def show

puts "Value of first Constant is #{VAR1}"

puts "Value of second Constant is #{VAR2}"

end

end

# Create Objects

object=Example.new()

object.show

Here VAR1 and VAR2 are constant. This will produce following result:

Value of first Constant is 100

Value of second Constant is 200

Ruby Pseudo-Variables:

They are special variables that have the appearance of local variables but behave like constants. You can not assign any value to these variables.

*

self: The receiver object of the current method.

*

true: Value representing true.

*

false: Value representing false.

*

nil: Value representing undefined.

*

__FILE__: The name of the current source file.

*

__LINE__: The current line number in the source file.

Ruby Basic Literals:

The rules Ruby uses for literals are simple and intuitive. This section explains all basic Ruby Literals.

Integer Numbers:

Ruby supports integer numbers. An integer number can range from -230 to 230-1 or -262 to 262-1. Integers with-in this range are objects of class Fixnum and integers outside this range are stored in objects of class Bignum.

You write integers using an optional leading sign, an optional base indicator (0 for octal, 0x for hex, or 0b for binary), followed by a string of digits in the appropriate base. Underscore characters are ignored in the digit string.

You can also get the integer value corresponding to an ASCII character or escape sequence by preceding it with a question mark.

Example:

123 # Fixnum decimal

1_234 # Fixnum decimal with underline

-500 # Negative Fixnum

0377 # octal

0xff # hexadecimal

0b1011 # binary

?a # character code for 'a'

?\n # code for a newline (0x0a)

12345678901234567890 # Bignum

NOTE: Class and Objects are explained in a separate chapter of this tutorial.

Floating Numbers:

Ruby supports integer numbers. They are also numbers but with decimals. Floating-point numbers are objects of class Float and can be any of the following:

Example:

123.4 # floating point value

1.0e6 # scientific notation

4E20 # dot not required

4e+20 # sign before exponential

String Literals:

Ruby strings are simply sequences of 8-bit bytes and they are objects of class String. Double-quoted strings allow substitution and backslash notation but single-quoted strings don't allow substitution and allow backslash notation only for \\ and \'

Example:

#!/usr/bin/ruby -w

puts 'escape using "\\"';

puts 'That\'s right';

This will produce following result:

escape using "\"

That's right

You can substitute the value of any Ruby expression into a string using the sequence #{ expr }. Here expr could be any ruby expression.

#!/usr/bin/ruby -w

puts "Multiplication Value : #{24*60*60}";

This will produce following result:

Multiplication Value : 86400

Backslash Notations:

Following is the list of Backslash notations supported by Ruby:

Notation Character represented

\n Newline (0x0a)

\r Carriage return (0x0d)

\f Formfeed (0x0c)

\b Backspace (0x08)

\a Bell (0x07)

\e Escape (0x1b)

\s Space (0x20)

\nnn Octal notation (n being 0-7)

\xnn Hexadecimal notation (n being 0-9, a-f, or A-F)

\cx, \C-x Control-x

\M-x Meta-x (c | 0x80)

\M-\C-x Meta-Control-x

\x Character x

For more detail on Ruby Strings, go through Ruby Strings.

Ruby Arrays:

Literals of Ruby Array are created by placing a comma-separated series of object references between square brackets. A trailing comma is ignored.

Example:

#!/usr/bin/ruby

ary = [ "fred", 10, 3.14, "This is a string", "last element", ]

ary.each do |i|

puts i

end

This will produce following result:

fred

10

3.14

This is a string

last element

For more detail on Ruby Arrays, go through Ruby Arrays.

Ruby Hashes:

A literal Ruby Hash is created by placing a list of key/value pairs between braces, with either a comma or the sequence => between the key and the value. A trailing comma is ignored.

Example:

#!/usr/bin/ruby

hsh = colors = { "red" => 0xf00, "green" => 0x0f0, "blue" => 0x00f }

hsh.each do |key, value|

print key, " is ", value, "\n"

end

This will produce following result:

green is 240

blue is 15

red is 3840

For more detail on Ruby Hashes, go through Ruby Hashes.

Ruby Ranges:

A Range represents an interval.a set of values with a start and an end. Ranges may be constructed using the s..e and s...e literals, or with Range.new.

Ranges constructed using .. run from the start to the end inclusively. Those created using ... exclude the end value. When used as an iterator, ranges return each value in the sequence.

A range (1..5) means it includes 1, 2, 3, 4, 5 values and a range (1...5) means it includes 1, 2, 3, 4 values.

Example:

#!/usr/bin/ruby

(10..15).each do |n|

print n, ' '

end

This will produce following result:

10 11 12 13 14 15

For more detail on Ruby Range

RUN Command in WINDOWS

Usefull Run Commands For Windows XP

Here is a list of commands that you can run off from the Run Command prompt in XP:

Program Run Command

Accessibility Controls = access.cpl

Accessibility Wizard = accwiz

Add Hardware Wizard = hdwwiz.cpl

Add/Remove Programs = appwiz.cpl

Administrative Tools = control admintools

Adobe Acrobat ( if installed ) = acrobat

Adobe Distiller ( if installed ) = acrodist

Adobe ImageReady ( if installed ) = imageready

Adobe Photoshop ( if installed ) = photoshop

Automatic Updates = wuaucpl.cpl

Basic Media Player = mplay32

Bluetooth Transfer Wizard = fsquirt

Calculator = calc

Ccleaner ( if installed ) = ccleaner

C: Drive = c:

Certificate Manager = cdrtmgr.msc

Character Map = charmap

Check Disk Utility = chkdsk

Clipboard Viewer = clipbrd

Command Prompt = cmd

Command Prompt = command

Component Services = dcomcnfg

Computer Management = compmgmt.msc

Compare Files = comp

Control Panel = control

Create a shared folder Wizard = shrpubw

Date and Time Properties = timedate.cpl

DDE Shares = ddeshare

Device Manager = devmgmt.msc

Direct X Control Panel ( if installed ) = directx.cpl

Direct X Troubleshooter = dxdiag

Disk Cleanup Utility = cleanmgr

Disk Defragment = dfrg.msc

Disk Partition Manager = diskmgmt.msc

Display Properties = control desktop

Display Properties = desk.cpl

Display Properties (w/Appearance Tab Preselected ) = control color

Dr. Watson System Troubleshooting Utility = drwtsn32

Driver Verifier Utility = verifier

Ethereal ( if installed ) = ethereal

Event Viewer = eventvwr.msc

Files and Settings Transfer Tool = migwiz

File Signature Verification Tool = sigverif

Findfast = findfast.cpl

Firefox = firefox

Folders Properties = control folders

Fonts = fonts

Fonts Folder = fonts

Free Cell Card Game = freecell

Game Controllers = joy.cpl

Group Policy Editor ( xp pro ) = gpedit.msc

Hearts Card Game = mshearts

Help and Support = helpctr

Hyperterminal = hypertrm

Hotline Client = hotlineclient

Iexpress Wizard = iexpress

Indexing Service = ciadv.msc

Internet Connection Wizard = icwonn1

Internet Properties = inetcpl.cpl

Internet Setup Wizard = inetwiz

IP Configuration (Display Connection Configuration) = ipconfig /all

IP Configuration (Display DNS Cache Contents) = ipconfig /displaydns

IP Configuration (Delete DNS Cache Contents) = ipconfig /flushdns

IP Configuration (Release All Connections) = ipconfig /release

IP Configuration (Renew All Connections) = ipconfig /renew

IP Configuration (Refreshes DHCP & Re-Registers DNS) = ipconfig /registerdns

IP Configuration (Display DHCP Class ID) = ipconfig /showclassid

IP Configuration (Modifies DHCP Class ID) = ipconfig /setclassid

Java Control Panel ( if installed ) = jpicpl32.cpl

Java Control Panel ( if installed ) = javaws

Keyboard Properties = control keyboard

Local Security Settings = secpol.msc

Local Users and Groups = lusrmgr.msc

Logs You Out of Windows = logoff

Malicious Software Removal Tool = mrt

Microsoft Access ( if installed ) = access.cpl

Microsoft Chat = winchat

Microsoft Excel ( if installed ) = excel

Microsoft Diskpart = diskpart

Microsoft Frontpage ( if installed ) = frontpg

Microsoft Movie Maker = moviemk

Microsoft Management Console = mmc

Microsoft Narrator = narrator

Microsoft Paint = mspaint

Microsoft Powerpoint = powerpnt

Microsoft Word ( if installed ) = winword

Microsoft Syncronization Tool = mobsync

Minesweeper Game = winmine

Mouse Properties = control mouse

Mouse Properties = main.cpl

MS-Dos Editor = edit

MS-Dos FTP = ftp

Nero ( if installed ) = nero

Netmeeting = conf

Network Connections = control netconnections

Network Connections = ncpa.cpl

Network Setup Wizard = netsetup.cpl

Notepad = notepad

Nview Desktop Manager ( if installed ) = nvtuicpl.cpl

Object Packager = packager

ODBC Data Source Administrator = odbccp32

ODBC Data Source Administrator = odbccp32.cpl

On Screen Keyboard = osk

Opens AC3 Filter ( if installed ) = ac3filter.cpl

Outlook Express = msimn

Paint = pbrush

Password Properties = password.cpl

Performance Monitor = perfmon.msc

Performance Monitor = perfmon

Phone and Modem Options = telephon.cpl

Phone Dialer = dialer

Pinball Game = pinball

Power Configuration = powercfg.cpl

Printers and Faxes = control printers

Printers Folder = printers

Private Characters Editor = eudcedit

Quicktime ( if installed ) = quicktime.cpl

Quicktime Player ( if installed ) = quicktimeplayer

Real Player ( if installed ) = realplay

Regional Settings = intl.cpl

Registry Editor = regedit

Registry Editor = regedit32

Remote Access Phonebook = rasphone

Remote Desktop = mstsc

Removable Storage = ntmsmgr.msc

Removable Storage Operator Requests = ntmsoprq.msc

Resultant Set of Policy ( xp pro ) = rsop.msc

Scanners and Cameras = sticpl.cpl

Scheduled Tasks = control schedtasks

Security Center = wscui.cpl

Services = services.msc

Shared Folders = fsmgmt.msc

Sharing Session = rtcshare

Shuts Down Windows = shutdown

Sounds Recorder = sndrec32

Sounds and Audio = mmsys.cpl

Spider Solitare Card Game = spider

SQL Client Configuration = clicongf

System Configuration Editor = sysedit

System Configuration Utility = msconfig

System File Checker Utility ( Scan Immediately ) = sfc /scannow

System File Checker Utility ( Scan Once At Next Boot ) = sfc /scanonce

System File Checker Utility ( Scan On Every Boot ) = sfc /scanboot

System File Checker Utility ( Return to Default Settings) = sfc /revert

System File Checker Utility ( Purge File Cache ) = sfc /purgecache

System File Checker Utility ( Set Cache Size to Size x ) = sfc /cachesize=x

System Information = msinfo32

System Properties = sysdm.cpl

Task Manager = taskmgr

TCP Tester = tcptest

Telnet Client = telnet

Tweak UI ( if installed ) = tweakui

User Account Management = nusrmgr.cpl

Utility Manager = utilman

Volume Serial Number for C: = label

Volume Control = sndvol32

Windows Address Book = wab

Windows Address Book Import Utility = wabmig

Windows Backup Utility ( if installed ) = ntbackup

Windows Explorer = explorer

Windows Firewall = firewall.cpl

Windows Installer Details = msiexec

Windows Magnifier = magnify

Windows Management Infrastructure = wmimgmt.msc

Windows Media Player = wmplayer

Windows Messenger = msnsgs

Windows Picture Import Wizard (Need camera connected) = wiaacmgr

Windows System Security Tool = syskey

Windows Script host settings = wscript

Widnows Update Launches = wupdmgr

Windows Version ( shows your windows version ) = winver

Windows XP Tour Wizard = tourstart

Wordpad = write

Zoom Utility = igfxzoom

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