Suggest an appropriate recovery technique that a database administrator could us

Question

Suggest an appropriate recovery technique that a database administrator could use to resolve each of the following situations.

a. A network disconnection occurs while a user is entering a transaction at an ATM bank machine.

b. A disk drive fails during regular operations while a clerk is entering data about newly registered students.

c. The registration office at a university entered an incorrect amount for a student tuition payment. The error was discovered by the financial services department several weeks later.

d. The database administrator of a financial institution performed a full database backup, but forgot to activate the journalizing facility. Afterwards, data entry clerks at the financial institution entered transactions for two hours before the database became corrupt. It is discovered that the journalizing facility of the database has not been activated since the backup was made.

Explanation / Answer

a) It is a type of Aborted Transaction. Use Backward recovery . The transaction can be reapplied if necessary or if the intent was to abort the transaction, then the rollback resolves all issues.

b) This is a type of Database destruction. Here forward recovery from the last good backup can be used to restore to a new server.

c) If the fee is already paid by the student then, an offsetting transaction, i.e a credit can be made against the account to be posted. If payment is not yet made, then we can use backward discovery.

d) Rollback to the last available checkpoint and redo the transactions again.

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