SQL, From this case I need answer for letter E and H only E.- Is it possible for

Question

SQL, From this case I need answer for letter E and H only

E.- Is it possible for deadlock to occur between two Sale Transactions? Why or why not? Is it possible for deadlock to occur between a Sale Transaction and an Item Quantity Received Transaction? Why or why not?

H.-The Queen Anne Curiosity Shop has developed the following procedure for backup and recovery. The company backs up the entire database from the server to a tape every Saturday night. The tapes are taken to a safety deposit box at a local bank on the following Thursday. Printed paper records of all sales are kept for 5 years. If the database is ever lost, the plan is to restore the database from the last full backup and reprocess all the sales records. Do you think this backup and recovery program is sufficient for the Queen Anne Curiosity Shop? What problems might occur? What alternatives exist? Describe any changes you think the company should make to this system.

Explanation / Answer

E.
Deadlock will not occur between two sales transactions. Because two are different with the different saleID 's , though these two transactions needs to update the same table. The first transaction which acquires the lock on table will release after it succesfully updates and then the second transaction. There is no possibility to occur the deadlock.

No even between the sale transaction and the ItemQuantity received transaction deadlock not occur because if the ItemQuantityReceived is acquired lock first then it will update the stock and then exits then the sale transaction will execute and decreases the quantity on hand according to the sale and vice versa. Because for both of these transactions are different with each other but trying to access the same attribute so one after other doing updations poses no deadlocks.

H.
This backup strategy doesn't satisfy or sufficient for the Queen Anne Curiosity Shop or doesn't meet its requirements. Because when the system is lost it will get only the backup performed on the previous saturday night which means the sales records untill the last saturday only. i.e. if the system is lost on wednesday the sales transactions from sunday to wednesday is lost even when we do the backup this backup contains the sales transactions untill the saturday night only. The transactions from after that full backup and before the system lost will not be stored any where this causes data loss and system inconsistency.
To avoid this we need to setup new backup startegy which is Incremental backup strategy to be implemented along side with the full backup strategy.
Incremental backup means it takes backups of those files which are updated only those files after the last full backup means that all the transactions from sunday to before the system lost will be backed up by incremental backup. So when we restore the backup we need to give both the full backup and these incremental backup then all the data will be restored to the system.

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