What is Lost Update Problem in DBMS?

In a schedule, if update performed by transaction T1 on data item ‘X’ gets overwritten by the update performed by transaction T2 on same data item ‘X’, then we say that update of T1 is lost to the update of T2.

This problem is known as Lost-Update-Problem in concurrent schedules.

Example:

with X = 50 and Y =50 (initial values)

T1T2
read(x) (T1I1)
x=x+10 (T1I2)
read(x) (T2I1)
x=x+20 (T2I2)
write(x) (T1I3)
read(y) (T1I4)
write(x) (T2I2)
commit (T2I2)
y=y+10 (T1I5)
write(y) (T1I6)
commit (T1I7)

Explanation:

Continue reading “What is Lost Update Problem in DBMS?”
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Serial Schedules, Concurrent Schedules and Conflict Operations

A schedule is the representation of execution sequence for all the instructions of the transactions. Schedules are categorized in two types:

  • Serial Schedules
  • Concurrent Schedules

Serial Schedules:

A schedule is said to be serial if and only if all the instructions of all the transactions get executed non-preemptively as an unit. OR

Each serial schedule consists of a sequence of instructions from various transactions, where the instructions belonging to one single transaction appear together in that schedule.

Continue reading “Serial Schedules, Concurrent Schedules and Conflict Operations”

Concurrent Execution in Transaction | DBMS

Transaction-processing systems usually allow multiple transactions to run concurrently. Allowing multiple transactions to update data concurrently causes several complications with consistency of the data.

Ensuring consistency in spite of concurrent execution of transactions requires extra work; it is far easier to insist that transactions run serially—that is, one at a time, each starting only after the previous one has completed.

Continue reading “Concurrent Execution in Transaction | DBMS”

Difference between Normalization and Normal Forms

Normalization:

Normalization is the systematic process applied on the relations to reduce the degree of redundancy.

Normalization is defined as systematic because it always gives guarantee for following properties –

  • Lossless decomposition.
  • Dependency preservation.
Continue reading “Difference between Normalization and Normal Forms”

Implementation of Atomicity and Durability using Shadow Copy

The recovery-management component of a database system can support atomicity and durability by a variety of schemes.

Here we are going to learn about one of the simplest scheme called Shadow copy.

Shadow copy:

Continue reading “Implementation of Atomicity and Durability using Shadow Copy”

Convert local path to UNC (Universal) File Path using Java Script ActiveXObject


<script>

function getUNCPath() {
var filePath = document.getElementById("uploadedFile").value;

var WshNetwork = new ActiveXObject("WScript.Network");
var Drives = WshNetwork.EnumNetworkDrives();
for (i = 0; i < Drives.length; i += 2) {
if(Drives.Item(i) != "")
{
if(filePath.match("^"+Drives.Item(i))){
filePath = filePath.replace(Drives.Item(i), Drives.Item(i + 1));
break;
}
}}
}

</script>

<form onsubmit="getUNCPath()">
<input type="file" id="uploadedFile"/>
<input type="submit" value="Get the UNC Path!" />
</form>

in razor view engine add the following line to support ActiveXObject:

@using System.Web.Script.Serialization

DBMS Notes for GATE 2020

Types of Functional Dependencies in Normalization

FD

Functional Dependency:

In Relational database, Functional dependency is denoted as X -> Y where X:Determinant and Y: Dependent. So, as per the concept the value of Y gets determined by the value of X.

If value of X gets duplicated, then in those rows value of Y shall also gets duplicated correspondingly.

If the determinant X value is unique (different) then the dependent Y could have any value meaning:

  • For same X , value of Y should be same.
  • For different X, value of Y could be same or different.

Continue reading……..

Difference between DBMS and RDBMS

DBMSVsRDBMS.png

How To Redirect HTTP to HTTPS using C#

HttpToHTTPs

Hello Readers,

While developing web application many of us must have observed that after deploying to web server, web page url starts with http but not the secured one https.

So if we want to redirect url from HTTP to HTTPS there is a very simple solution in C#.

Just copy and paste the below code in your “Global.asax.cs” file and you are all done.

Continue reading “How To Redirect HTTP to HTTPS using C#”

What’s new in .NET Framework 4.7.1 (Part 3)

New Release .NET Framework 4.7.1

Hello Readers,

This post is in continuation with “What’s new in .NET Framework 4.7.1 Part 2“.

[Whats new in .Net Framework 4.7.1 Part 1,Whats new in .Net Framework 4.7.1 Part 2]

New Features includes:

WPF – Changing implicit data templates 

  • This feature enables the automatic update of elements that use implicit DataTemplates after changing a resource.
  • When an application adds, removes, or replaces a value declared in a ResourceDictionary, WPF automatically updates all elements that use the value in most cases, including the implicit style case:<Style TargetType=”Button”.
Continue reading “What’s new in .NET Framework 4.7.1 (Part 3)”

What’s new in .NET Framework 4.7.1 (Part 2)

New Release .NET Framework 4.7.1

Hello Readers,

This post is in continuation with “What’s new in .NET Framework 4.7.1 Part 1“.

New Features includes:

Accessibility improvements

.NET Framework 4.7.1 brings in a lot of accessibility improvements across different libraries to align with the broad Microsoft product accessibility goals. 

Windows Forms Accessibility improvements

Windows Forms accessibility changes are in the following areas:

  • Improved display during High Contrast mode
  • Enhanced UI accessibility patterns
  • Improved UI Accessibility properties with the outcome of improved experiences in accessibility tools like Narrator

High Contrast Improvements

Various controls in WinForms are now improved in the way they render under the various HighContrast modes available in the Operating System (OS).

Continue reading “What’s new in .NET Framework 4.7.1 (Part 2)”