Class : MCA 2nd (2014 - 2015)

Topics : Transection System Concepts

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By : Mr Jitendra Thakur

TRANSECTION

SYSTEM CONCEPTS

» Introduction :

» Operation of Transaction :

» Properties of Transaction :

» Transaction System State :

» Explanation :

» Transaction Process System :

» Recovery from Transaction Failure :

» Types of Failure :

» Recovery Method :

» Example :

» Recoverably Schedule :

» Example :

» Thank you :

» Collection of operation that from a single

logical unit of work is called transection

» A transection is a unit of program

execution that access and possibly obtain

various data item

» Main operation of transection :

I. Read (X) ; -which transfer the data item X

from the data base to a logical buffer

belonging to a transection that execute the

read operation

II. Write (x); -which transfer the data item from

the logical buffer of the transection that

executed if write back to the data base

» Transection have 4 properties : likely

» ACID TEST

I. Atomicity

II. Consistency

III. Isolation

IV.Durability –after commit it will be stable

Partially committ

ed

Failed

Committed

Aborted

Active

» Active – it’s the initial state ,the transection stay

in this state while its executed .

» Partially(not permanent save ) committed – after

the final statement has been executed .

» Aborted – after the transection has been role

back and the data base has been restored .

» Committed – a transection that complete its

execution successfully is said to be committed .

» Failed – after the discovery that normal

execution can be longer processed .

TPS are the system which include large size data base and

allow many users to use same data base concurrently

Example 1-railway reservation system

2-credit card system

Other similar system is called TPS .

» Computer like any other device to subject to

failure include power failure disk crash software

error etc

» In this case the database patterning the database

is lost

» Lose of volatize storage –log based recovery ,

buffered management , check points and

pshadaw paging techniques.

» Non volatize storage lose – hard disk ,magnetic

disk and tape ,if a failure occur the data is used

in restoring concept in the data base

» Cascading recovery (roll back )- a single

transaction failure follow a series of transaction

roll back is called cascading roll back .

» If T1 is failure then the all series of transaction

will be failed because hare in this ex T3 is

depend on T2 and T2 depend on T1.

» T1 T2 T3

» Read (x);

» Read(y);

» Z=x+y;

» Write(z);

--------------------------------------------------------------» Read (z);

» Write(z);

---------------------------------Read(z)

Depend Depend

» In this schedule T3 transaction perform only one

transaction read(z)

» T3 is not dependent to transaction T1 and T2

» All transaction work as a separately .

» Not depend with each others.

» Consider following example .

» T1 T2 T3

» Read(x);

» Write(x);

» ----------------------------------------------------------------

» Read(x);

------------------------------------------

Read(x);

(committed)

Independent Independent