CSCI 475 Ch. 10

Question 1

ACID stands for

Answer 1

atomicity, consistency, isolation, durability

Question 2

atomicity means that

Answer 2

all operations of a transaction must be completed

Question 3

consistency refers to the

Answer 3

permanence of database’s consistent state

Question 4

isolation means

Answer 4

data used during a transaction cannot be used by a second transaction until the first is completed

Question 5

durability ensures that

Answer 5

once transactions are committed, they cannot be undone or lost

Question 6

transaction format when updating

Answer 6

BEGIN;

UPDATE [table]
SET [whatever]
WHERE [whatever];

COMMIT;

Question 7

transaction format when inserting and updating

Answer 7

BEGIN;

INSERT INTO [table] VALUES (whatever);

UPDATE [table]
SET [whatever]
WHERE [whatever];

COMMIT;

Question 8

lost update occurs when

Answer 8

both transactions write but one write is lost (both read and operate on the original value)

Question 9

uncommitted data occurs when

Answer 9

a second transaction reads what a first has written before the first decides to rollback (ex: T1 updates quantity from 5 to 10, T2 reads the written value of 10 (no T1 commit) and proceeds, T1 rollback, T2 commit)

Question 10

inconsistent retrieval occurs when

Answer 10

data is read at different points during another transaction (ex: T1 updates three values by adding 5 - T2 reads value A after 5 has been added, but reads values B and C before 5 has been added)