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Articles by Bhanu Priya
Page 82 of 106
What are hashed files and indexed file organization(DBMS)?
Let us begin by understanding the hashed file organisation.Hashed File OrganisationHashed file organisation is also called a direct file organisation.In this method, for storing the records a hash function is calculated, which provides the address of the block to store the record. Any type of mathematical function can be used as a hash function. It can be simple or complex.Hash function is applied to columns or attributes to get the block address. The records are stored randomly. So, it is also known as Direct or Random file organization.If the generated hash function is on the column which is considered as ...
Read MoreWhat is the common source of database failure?
Database failure is a quite common problem of information technology. It can occur even with good database system software. There may be a simple error which can lead to loss of the complete database.Causes of database failureSome of the causes for database failure are as follows −Database file corruptionIf a file in the database is corrupted or damaged, it can lead to the database failure. The file can become corrupt due to the following reasons −Changes in the SQL Server account.Accidental data deletion.File header corruption.Errors in accessing the data.InterruptionWhen the server or computer is not shut down properly or during ...
Read MoreWhat is OLAP? Explain its advantages and disadvantages
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 MoreWhat are the Database recovery techniques?
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 MoreWhat are different transaction isolation levels in DBMS?
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 MoreExplain the concept of recoverability in DBMS
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 MoreWhat are the different types of schedules in DBMS?
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 MoreWhat is RAID in DBMS?
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 MoreExplain the concept of magnetic disk with the help of a diagram(DBMS)
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 MoreWhat is shadow paging in DBMS?
Shadow paging is one of the techniques that is used to recover from failure. We all know that recovery means to get back the information, which is lost. It helps to maintain database consistency in case of failure.Concept of shadow pagingNow let see the concept of shadow paging step by step −Step 1 − Page is a segment of memory. Page table is an index of pages. Each table entry points to a page on the disk.Step 2 − Two page tables are used during the life of a transaction: the current page table and the shadow page table. Shadow ...
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