Found 1721 Articles for Big Data Analytics

What is OLAP? Explain its advantages and disadvantages

Bhanu Priya
Updated on 08-Jul-2021 07:17:43

5K+ Views

OLAP represents online insightful handling and can be characterized as: "Online logical preparation alludes to an assortment of exercises typically performed by End-clients in the online framework."OLAP incorporates choice help, demonstrating, data recovery, impromptu detailing, and imagining a scenario in which investigation. OLAP focuses on choice help needs.ERP framework is a choice help instrument that gives constant data to the board and permits the executives to make convenient choices based on that data that is expected to improve execution and to accomplish determined objectives.Example of OLAPThe case of OLAP can be consolidating deals information by deals channel, item type, and ... Read More

What are the Database recovery techniques?

Bhanu Priya
Updated on 08-Jul-2021 07:13:51

13K+ Views

Database systems which are similar to some different PC frameworks, are mainly dependent upon disappointments however the information put away in it should be accessible as and when required. At that point, when an information base bombs it should have the offices for quick recuperation. It should likewise have atomicity, For example, either exchanges are finished effectively and submitted (the impact is recorded for all time in the information base) or the exchange ought to have no impact on the data set.There are both programmed and non-programmed ways for both, backing up information and recuperation from any disappointing circumstances. The ... Read More

What are different transaction isolation levels in DBMS?

Bhanu Priya
Updated on 08-Jul-2021 07:11:43

6K+ Views

In case of transaction the term ACID has been used significantly to state some of important properties that a transaction must follow. We all know ACID stands for Atomicity, Consistency, Isolation and Durability and these properties collectively called as ACID Properties.Properties of transactionDatabase system ensures ACID property −Atomicity − Either all or none of the transaction operation is done.Consistency − A transaction transfer from one consistent (correct) state to another consistent state.Isolation − A transaction is isolated from other transactions. i.e. A transaction is not affected by another transaction. Although multiple transactions execute concurrently it must appear as if the ... Read More

Explain the precedence graph for testing conflict serializability(DBMS)

Bhanu Priya
Updated on 08-Jul-2021 07:09:34

2K+ Views

Conflict serializability orders any conflicting operations in the same way as some serial execution. A pair of operations is said to conflict if they operate on the same data item and one of them is a write operation.That means, Readi(x) readj(x) - non conflict read-read operationReadi(x) writej(x) - conflict read-write operation.Writei(x) readj(x) - conflict write-read operation.Writei(x) writej(x) - conflict write-write operation.Where, I and j denote two different transactions Ti and Tj.Precedence graphNow consider a precedence graph for testing conflict serializability. It is used to check conflict serializability.Steps for precedence graphFor each transaction T, put a node or vertex in the ... Read More

Check whether two schedules are view equal or not(DBMS)

Bhanu Priya
Updated on 08-Jul-2021 07:07:23

291 Views

There are two types of serializability which are as follows −View serializabilityA schedule is view-serializability if it is view equivalent to a serial schedule.The rules it follows are given below −T1 is reading the initial value of A, and then T2 also reads the initial value of A.T1 is the reading value written by T2, and then T2 also reads the value written by T1.T1 is writing the final value, and then T2 also has the write operation as the final value.Conflict serializabilityIt orders any conflicting operations in the same way as some serial execution. A pair of operations is ... Read More

Explain the concept of recoverability in DBMS

Bhanu Priya
Updated on 08-Jul-2021 07:05:32

8K+ Views

The characteristics of non-serializable schedules are as follows −The transactions may or may not be consistent.The transactions may or may not be recoverable.So, now let’s talk about recoverability schedules.We all know that recoverable and irrecoverable are non-serializable techniques, Irrecoverable schedulesIf a transaction does a dirty read operation from an uncommitted transaction and commits before the transaction from where it has read the value, then such a schedule is called an irrecoverable schedule.ExampleLet us consider a two transaction schedules as shown below −T1T2Read(A)Write(A)-Read(A) ///Dirty Read-Write(A)-Commit-RollbackThe above schedule is a irrecoverable because of the reasons mentioned below −The transaction T2 which is ... Read More

What is dirty read in a transaction(DBMS)?

Bhanu Priya
Updated on 08-Jul-2021 07:03:35

9K+ Views

When many transactions are executed simultaneously then we call them concurrent transactions. Concurrency is required to increase time efficiency. If there are many transactions which are trying to access the same data, then inconsistency arises. Concurrency control is required to maintain consistency of data.In order to run transactions concurrently, we interleave their operations. Each transaction gets a share of computing time.Problems in transactionsThis leads to the following problems −Lost update problem. ( WW conflict)Dirty read / temporary update. ( WR conflict)Unrepeatable read / incorrect analysis problem. (RW conflict)All these arise because isolation is broken.Let us discuss the dirty read or ... Read More

What are the different types of schedules in DBMS?

Bhanu Priya
Updated on 08-Jul-2021 07:01:09

13K+ Views

A schedule is defined as an execution sequence of transactions. A schedule maintains the order of the operation in each individual transaction. A schedule is the arrangement of transaction operations. A schedule may contain a set of transactions. We already know that a transaction is a set of operations. To run transactions concurrently, we arrange or schedule their operations in an interleaved fashion.Schedules are divided into 2 categories, which are as follows −Serial ScheduleNon-serial ScheduleThe categories of schedules are given below in a form of chart −Serial scheduleTransactions present in this schedule are executed serially, after the instruction of Ti ... Read More

What is RAID in DBMS?

Bhanu Priya
Updated on 08-Jul-2021 06:56:39

15K+ Views

Redundant Array of Independent Disk (RAID) combines multiple small, inexpensive disk drives into an array of disk drives which yields performance more than that of a Single Large Expensive Drive (SLED). RAID is also called Redundant Array of Inexpensive Disks.Storing the same data in different disk increases the fault-tolerance.The array of Mean Time Between Failure (MTBF) = MTBF of an individual drive, which is divided by the number of drives in the array. Because of this reason, the MTBF of an array of drives are too low for many application requirements.Types of RAIDThe various types of RAID are explained below ... Read More

Explain the concept of magnetic disk with the help of a diagram(DBMS)

Bhanu Priya
Updated on 08-Jul-2021 06:53:04

3K+ Views

Magnetic disk is the secondary storage device used to support direct access to a desired location.Parts in Magnetic diskThe different parts that are present in magnetic disk or hard disk are explained below. All these parts are helpful to read, write and store the data in the hard disk.Disk blocks − The unit data transfer between disk and main memory is a block. A disk block is a contiguous sequence of bytes.Track − Blocks are arranged in concentric rings called tracks.Sectors − A sector is the smallest unit of information that can be read from or written to disk: for ... Read More

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