recovery management

recovery management

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