This document discusses recovery management and concurrency controls in databases. It defines recovery management as the process of restoring a database to its most recent consistent state after a failure. There are three states in recovery: pre-condition (consistent), condition (failure occurs), and post-condition (restore to pre-failure state). The types of failures are transaction, system, and media failures. Concurrency control manages simultaneous transactions to maintain consistency and prevent issues like lost updates, temporary updates, and incorrect summaries that can occur from concurrent execution.

1. Recovery management with
concurrent controls
D. Shanmugapriya
II-Msc (IT)
Department of CS & IT
Nadar saraswathi college of arts and science
Theni.

2. Recovery Management
• Recovery manager is a utility that manages the
process of creating backups of all database files.
• Is the process of restoring the database to the most
recent consistent state that existed just failure the
system.
• Is the process of planning,testing and
implementing the recovery procedures and
standards required to restore service in the event
of a component failure.

3. 3 states of recovery
• Pre-condition:In a consistant state.
• Condition:Occurs some kind of system failure.
• Post condition:Restore the data base to the
consistent state of the existed before the failure.

4. Types
• Transaction failure :Occurs when it fails to execute or when
it reaches a point from where it can’t go any further. If a
few transaction is hurt this is called as transaction
failure.(incorrect IP, deadlock)
• System failure :May result from a hard drive with bad
sectors, causing the operating system to not able to read
data from the hard drive. (is failure, ram failure).
• Media failure :A condition of not being able to read from
or write to a storage device such as a disk or tape due to a
defect in the recording surface. (power problem).

5. Database basic update strategies
• Deferred update:Transaction operating do not immediately
update the physical database.
• Database is physically updated only after the transaction
reaches it’s commit point.
• Immediate update:database is immediately updated by
the transaction operation during the execution of
transactions even before it reaches commit point.
• Example :word-to save the file and immediately updated.

6. Concurrent control
• The process of managing simultaneous operation on the
database without having them interface with each other.
• The problem of synchronizing concurrent transaction
such that the consistency of the database of the
maintained same time.
• Concurrent controls invlove identifying and preventing
problems in a organizing as they occur this means that as
they occur.

7. Why we need concurrency control
• Simultaneous execution of transaction over a shared
database can create several data integrity and consistency
problem.
• Three types
• 1)lost update
• 2)temporary uodate
• 3)incorrect summary

8. Lost update
• This problem occurs when two transactions that access
the same database items.
• Have their operation interlaced in a way that makes the
values of same database item incorrect.
• Successfully completed update is overridden by another
user.
• Example:T1 withdraws $10 from an account with
balance initially $ 100.
• T2 deposits $100 into same accoint
• Serially final balance would be $190.

9. Temporary update
• This problem occurs when one transaction updates a
database item and then the transaction fails for some
reasons.
• The updated item is accessed by another transactions
before it is changed back to its original value.
• Example :T4 updates balance to 200 but it aborts so
balance should be back at original value 100
• T3 has read new value of balance 200 and users value as
basis of 10 reduction giving a new balance of 190 instead
of 90.

10. Advantage
• Waiting time decrease
• Response time decrease.
• Resourse utilization increase.
• Efficiency utilization increase.

11. Thank you