Abstraction means giving on overall view of the system without bothering for intricacies of system within. A database abstraction is an abstraction for the user such that user is able to handle the same without going into the details of the database system. Database abstraction, this way, in an application programming interface (API) that establishes communication between a user-oriented computer application and databases. Examples of such API are MySQL, PostgreSQL, Oracle, SQLite etc. Database vendors supply their own interface compatible with their products. To make it compatible with other database application programmers develop code for other database interfaces that is to be supported. This form layers that reduce burden for users, by providing an API and hide database internal behind this interface. As far as possible, user is kept free from bothering about the internals of the database.

Numerous abstraction layer are created with different interface is different programming languages. Oriented database system (ODBS) is an examples of a database abstraction layer for language. It is a database abstraction layer which is platform-independent. The user is required to install a particular drive- software, enabling ODBC to communicate with a database or set or databases. Thus program can also increase as statements are to be transformed into constructs understood by the target database.

Data in DBMS has three levels of abstraction. These are conceptual, physical and external schemas. A data definition language (DDL) defines the external schemas.

Data abstraction hides the complexity by creating an intermediates structure, called middleware, which is better organized. This creates an application that makes requests for data in well- organized an logical formate and thus user is made free from the burden of knowing its actual physical layout. This is like a person going to purchase few medicine with a list without bothering about how it is kept physically in the store. Similarly a user handling an application may request fir a customers record from the data abstraction layers and it fetches data from various data sources and transforms these is an agreed logical structure and then returns to the calling application.

Recovery Control in distributed database is based on the two-phase commit protocol. The two phase commit protocol is the transaction protocol duo to which all nodes and databases agree with each other to commit a transaction. This protocol is required in an environment where single transaction can interact with multiple independent resource managers as in case of distributed databases. It also support data integrity by ensuring that modifications made to transactions are either committed by all the databases involved in teh distributed system or rolled back by all the databases.

The two phases commit protocol works in two phases. The first phase is called the prepare phase during which the updates are recorded in a transaction log file, and the resource through a resource manager indicates that it is ready to make the changes. Resources can vote either to commit phase depend on the vote of resources. If all resources vote to commit then, all the resources participating in the transaction are updated whereas if one or more of the resources vote to roll back, then, all the resources are rolled back to their previous state.

Consider an example, in which an interaction between a coordinator at a local site and a participant at a remote site takes place and a transaction has requested the commit operation. In the first phase, the coordinator instructs the participants to get ready and sends the get ready message at time. Participants make an entry in it log and send the ok message as acknowledgement to  the coordinator. The coordinator then, writes an entry in the log, takes a final decision and sends it to the participants.

FastStone Image Viewer Version 3.9 Software Review :

Where do you view your favourite images that you take with friends and families ? How do you enjoy navigating through various wallpapers that you have in your DVD ?
The basic tool that is available by default in Windows is the > Windows Image Viewer. In Windows Image Viewer, you can view an image to its actual size, rotate the image in the available angles, Zoom the image to view details, edit it in Windows Paint only, View many images in a slideshow, copy the selected file to a particular location, delete here directly, and print here directly. These features seem sufficient, but why settle with this when you have a lot more additional features available in the User friendly Image viewer software, FastStone Image Viewer ! The name simply says Image Viewer, but i think the the creators are being too modest about their work. It has a nice array of features that include image viewing, management, comparison, red-eye removal, emailing, resizing, cropping and color adjustments. Let me introduce to you, the COMMON features that are useful in performing everyday activities. This is a Combo pack of group of softwares like > Windows Image Viewer, Microsoft Powerpoint, Paint, Keyboard Print screen, etc. You can view images in the format Jpg, bmp, Cur, Gif, Ico, Pcx, Png, Psd, Tiff, Wmf, Camera Raw, etc.

Fastest Image Loading :

When i insert a DVD with say 200 wallpapers, it takes a lot of time for all the images to load completely, if you try to view the images by opening the folder containing the wallpapers in the DVD. It was very irritating, and i could not locate the desired picture i wanted because of the time taken to load. Later, when i tried to open the images in my external hard drive, because of the excellent quality of my hard drive, the images load very fast. How to load the images in the DVD and view them in the same manner as that of the hard drive ? The solution is the FastStone Image Viewer software. The loading time is Excellent even compared to my hard drive. Whether you are loading from a CD, DVD, or a pen drive, containing thousands of high definition wallpapers, the speed is enormous and you will not regret it. I was very happy the first time i viewed it.

Browsing and Viewing Images made convenient :

There is a browse menu unlike, Windows image viewer, to directly browse to an available folder containing pictures. You do not have to individually locate for images to view them. There are two types of menus for brosing the folders. One is the Browser present at the light side containg all the drivers in the system and the folders and sub folders under them. This is very convenient. Another one is the Quick browser, where the list of drives and folders that have been opened in FastStone Image Viewer recently appear. This do not contain any list of drives if no drives are opened and you are using for the first time. Once you select the particular folder and lot of subfolders, appear and now you can view the images. You can view them in the form of Thumbnails or list view or list view with the details about the files. Once, you click an image file, its preview is available in the bottom left side corner. You can adjust the preview size also varying from 10 % to 1000 % ( it is not hundred but upto thousand percentage). Then you can click the Full screen option to view the images in the full screen. You can view them in the slideshow also and adjust the slide timings. There are over 150 transition effects for the images during slideshow. This you might have seen in Microsoft Powerpoint.Even during a slideshow, you can use various features.

Managing the Images Files :

You can select multiple files in a particular folder and use various functions when you right click them such as copying them and pasting them in different location. Deleting them by sending them to recycle bin. Email them, and the default email browser appears to directly send the file in mail. Directly print them with full page layout control. You can also acquire images from a scanner and manage them here. There is also a Select all option to select all the items to perform a particular action. You can also arrange the files in order of their names / size / type of file / Dimensions / and Date created. You can directly create a new folder in any drives or folders and move files.

Tools > Batch Image Converter and Rename :

Right click an image file and there is an option called Tools. Under that, you have few special types of tools.This is a very useful software to convert/rename large or small collections of images. The feature is called Batch convertor as you can convert a group of images in the form of a bundle rather than single image at a time in formats like *.bmp, *.gif, *.tiff, and *.png. You can also rename the files here. Not only that, you can also resize the files in Bulk here. Another interesting tool available is that, you can add the time and date to images like in photos and also alter existing details. There is also a tool called Compare, wher you can select more than one file to compare. This is useful if you want to compare the features of two images with little variations. You can directly set a particular file as wallpaper for Desktop here.

Adding effects and adjusting colors of images :

You can select a particular image file and sharpen or Blur the image, you can reduce the colors from 256 colors(full fledged color image) to two colors (Black and white), Very interesting feature is that, you can count the number of different colors used in a particular image file. Is that not fun ? You can convert the image to grey scale or negative form. You can add Drop shadows and also remove red eye from photos. There are also special effects like Edge detect, that remove the fill and enables only the edges, Bump map, Lens and Morph. I have included the results of these effects below.

Screen Capture :

This is the major advantage of this software. Instead of using the Print screen option in the keyboard and pasting them in paint and cropping them to remove the excess area, you can use the Screen capture option in FastStone Image Viewer. This option is available in the File menu. There are different methods of screen capture.

• Capture Foreground Window > This is to capture any window, (that is a program, or a folder or an image, anything) that is open and is present in the FRONT of all other open windows. Only one window that is present in front is captured.

• Capture Window / Object > This is to capture a particular window or a particular portion / component of a windoe like the title bar, or the browse bar etc. Try opening multiple windows to see the effect.

• Capture Rectangle region > You can manually select any rectangular region of a open window to capture.

• Capture Freehand Region > Instead of drawing a rectangle, tou can draw a freehand drawing including curves just like drawing with a pencil. The region within the drawn area is captured. The drawing should be closed drawing (all sides are closed and there is no opening). The captured image, can be either simply viewed in the FastStone Image Viewer, or stored in the Clipart to view them, or save it to a file in a particular folder / location. You can save the captured images in the format > Jpg, bmp, Cur, Gif, Ico, Pcx, Png, Psd, Tiff, and also Adobe Pdf file.

Additional Unique Features :

• Edit in External programs > In Windows Image Viewer you can edit it in Windows Paint only, Here, you can choose any software that is installed in your system to edit a particular image file. For example, select an image file and edit in a program like Photoshop directly from here, instead of opening Photoshop first and searching for the image file to edit.

• Draw Board > Select a file and in Edit menu, you will have an option called, Draw Board. This is like the Paint program available in Windows. You can add text and one additional feature it has compared to Paint is that you can add Drop shadows also.

• Crop Board > This option is also available in Edit menu. Using this, you can crop a particular part of an image and save that cropped part.

Hence, FastStone Image viewer is an All in one Pack for Imgae viewing, Screen capture, Photo adjustments, Album creation and slideshow.

How To Install Chrome OS - Complete Guide

and you might be asking, what is VMware?
Layman answer: Just like Virtual CD, its a virtual PC. and like you can insert cd images in virtual cd. you can install OS inside VMware. which means you can try mac while still being on windows.

so after downloading, install VMware. (normal click next etc.)

and extract .bz OS file using winrar

now fire up your virtual machine

and click new virtual machine

and click typical

then select I will install OS later and click next

after that choose linux ubuntu and then next

then name ur mahcine and spacify its location

after that give it some size. though it says 20 but it doesn't matters
we are gonna delete this anyway

now before finishing spacify ur hardware

Now this is imporant

go to network and unselect NAT and click bridge and opion below it as shown

i tried messing with resolution here.. though it didn;t work.
anyway i'll show u how to change later
so you can skip this step

here was something that i did.. though it didn't made any sense.
i was getting logging in error so i removed my CD-ROM and Floppy
and it worked..
so you might also wanna do same...
as shown below

ok alomst done
so click ok and finish

and you will notice new virtual pc is made..

no click its settings to load chrome

select that hard disk which we created earlier and remove it

click add
select new hard
and click next

click use existing hard.. and next

browse for your OS which u downloaded and select it and also convet it to new format
if it asks

click ok and go back
now we are good
make ur your hard size is 2.8GB (if not then u didn't loaded file properly)
and lets start this much awaited OS

Enter you login details (make a fake account just to be secure)

and bingo you are in

to full screen click here

and to access apps go here

and now to change resolution
press ALT+CTRL+T
and enter
/usr/bin/xrandr
this will show you the available resolutions
after that select one
/usr/bin/xrandr --size ABxYZ
and enter
exit
as shown below

---

so that was it...
here are some useful shortcuts:
http://dev.chromium.org/chromium-os/how-\74wbr\76tos-and-troubleshooti

ng/developer-faq#TO\74wbr\76C-Shortcut-Keys

---

FINAL TIPS
if it gives error during booting
make your your hard is at IDE 0:0
(go to machine setting>>harddisk >> advance)
if error still comes then go to ur virtual machine folder and image folder
and delete the .lck folders
e.g Chrome OS.vmx.lck

If it gives error then make sure you clicked bridge and not NAT
and also go to network connects and play around with these.
e.g i changed one to from 192.168.54.1 to 192.168.1.8
my pc also has same subnet (192.168.1.*)

hope it helps

THATS ALL