Transactions

Question 1

A __________ is a sequence of operations on database objects

Answer 1

transaction

Question 2

All operation in a transaction formed together is a single ________ _____

Answer 2

logical unit

Question 3

What are 5 states in the life-cycle of a transaction?

Answer 3

• Active
• Partially committed
• Failed
• Committed
• Aborted

Question 4

An active transaction is in ______ execution state

Answer 4

normal

Question 5

A partially committed transaction just had its _____ statement executed

Answer 5

last

Question 6

A failed transaction cannot _______

Answer 6

proceed

Question 7

An aborted transaction _____ _____ the database

Answer 7

rolls back

Question 8

A committed transaction _______ and its changes are ________

Answer 8

succeeded, permanent

Question 9

What is a schedule?

Answer 9

a sequence S of operations from a set of transactions

where the order of operations of each Ti is the same as in S

Question 10

When is a schedule serial?

Answer 10

All operations of each transaction are executed before or after all operations of another

Question 11

Concurrent execution _________ different transaction operations

Answer 11

interleaves

Question 12

Concurrent execution increases ________ and reduces ______ _____

Answer 12

throughput, response time

Question 13

What does ACID stand for?

Answer 13

Atomicity (all or nothing)
Consistency (DB good after transaction)
Isolation
Durability (changes persist)

Question 14

The only important operation in scheduling are _____ and ____

Answer 14

read, write

Question 15

When are two operation conflicting?

Answer 15

They refer to the same data item and one or more of them is a write

Question 16

Two consecutive ______________ operation can be swapped

Answer 16

non-conflicting

Question 17

A schedule is ______ ___________ it it can be turned into a serial schedule by a sequence of swaps

Answer 17

conflict serializable

Question 18

In a precedence graph, each node is a _________ and each edge is a _______

Answer 18

transaction, conflict

Question 19

A schedule is conflict serializable IFF graph is ______

Answer 19

acyclic

Question 20

If one transaction aborts, we _____ the other one

Answer 20

abort

Question 21

A schedule is unrecoverable if one T aborts and the other ______

Answer 21

commits

Question 22

A shared (read) lock can be acquired by ______ transactions

Answer 22

multiple

Question 23

An exclusive (read/write) lock can be required by only ____ transaction

Answer 23

one

Question 24

Two locks on the same data item are _________ of one of them is exclusive

Answer 24

conflicting

Question 25

In two phase locking, transactions cannot request additional locks once it ________ ____ _____

Answer 25

releases any lock

Question 26

Every schedule of committed transactions that follow 2PL is ______ _______-

Answer 26

conflict serializable

Question 27

In strict 2PL all locks held by a transaction are _________ when it aborts or commits

Answer 27

released

Question 28

Strict 2PL is always __________

Answer 28

recoverable

Question 29

A deadlock is a cycle of ____

Answer 29

waits

Question 30

An older transaction has higher _______

Answer 30

priority

Question 31

The higher priority transaction is never ______

Answer 31

aborted

Question 32

What is starvation?

Answer 32

a transaction keeps being aborted

because it never has su!ciently high priority

Question 33

What are two policies to prevent deadlocks?

Answer 33

• Wait-die

- Wound-wait

Question 34

In the wait-die policy, older Ts wait for younger Ts and younger Ts get ________

Answer 34

aborted

Question 35

In the wound-wait policy, older Ts abort the younger Ts and younger Ts ____

Answer 35

wait

Question 36

A ______ ___ _____ is obtained from a resource allocation graph

Answer 36

waits for graph

Question 37

Each cycle in a waits for graph represents a _________

Answer 37

deadlock

Question 38

What is ARIES?

Answer 38

a recovery algorithm used in major DBMSs