7. Recovery

Question 1

Transaction Failure

• ___ erros - Ex: Interna errors
• ___ errors - Ex: Deadlock

Answer 1

Logical

System

Question 2

System Failures

• ___ crash
• ___ Failure

Answer 2

System

Disk

Question 3

Recovery from failures

• Transaction needs to be undone if log contains ___, but does not contain ___ or___
• Transaction needs to be redone if log contains ___, and contains ___ or___

Answer 3

Start / commit or abbort

Start / commit or abbort

Question 4

Undo

Restores values of items updated by transaction to their ___ values and adds ___ to log

Answer 4

Older

Abort

Question 5

Redo

Sets values of items updated by transaction to their ___ values and adds ___ to log

Answer 5

New

Nothing

Question 6

Checkpoints
1- Output log from ___ to ___
2- Output all modified ___ to the ___
3- Write a chackpoint ___ to ___

Answer 6

RAM to stable storage
Bugger blocks to the disk
Log to stable storage

Question 7

Recovery Algorithm

• ___ and ___ during normal operation
• Recovery from failure with two phases:
  1. Redo phase: ___ updates of all transactions, whether they committed, aborted, or are incomplete
  2. Undo phase: ___ all incomplete transactions

Answer 7

Logging and Transaction rollback
Replay
Undo

Question 8

Log record buffering

Log records are buffered in ___, instead of being output directly to ___.

Answer 8

Main memory

Stable storage

Question 9

ARIES

• Every log record has a ___ (log sequence number
• Every ___ (block) contains LSN of the most recent log record that ___ the page
• Each log record contains a ___ to the previous log record of the same ___

Answer 9

LSN
Page / changed
Pointer / transaction

Question 10

Dirty page table
Contains one entry for each dirty ___ in the buffer that has a ___ (points to the first log record that made the page dirty)

Answer 10

Page

recLSN

Question 11

Transaction table

Contains one entry for each ___ that has a ___ (points to the last log record of the transaction)

Answer 11

Active transaction

lastLSN

Question 12

Checkpoints in ARIES

Writte ___ and ___ ( that has the contents of the dirty page table and transaction table)

Answer 12

begin_checkpoint

end_checkpoint

Question 13

Recovery in ARIES

1. ___: Identifies dirty pages in the buffer pool and active transactions at crash
2. ___: Repeats all actions
3. ___: Undoes the actions of transactions that did not commit

Answer 13

1. Analysis
2. Redo
3. Undo

Question 14

Compensation log record (CLR)

___ to the next action to be ___

Answer 14

Pointer

Undone