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CS 564 > Final Vocabulary > Flashcards

Final Vocabulary Flashcards

1
Q

row store

A

store next to each other
- traditional way
- disk -> files -> pages -> records

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2
Q

unordered heap files

A

records in no order

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3
Q

pid

A

page id
- the pages in a file

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4
Q

rid

A

record id
- the records on a page
- <page id, slot number>

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5
Q

storage hierarchy

A

primary storage, secondary storage, tertiary storage

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6
Q

primary storage

A

main memory (RAM) for currently used data

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7
Q

secondary storage

A

disk for the main database

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8
Q

tertiary storage

A

tapes for archiving older versions of the data

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9
Q

disk blocks

A

the unit data is stored and retrieved in

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10
Q

platter

A

circular hard surface on which data is stored by inducing magnetic changes

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11
Q

spindle

A

axis responsible for rotating platters

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12
Q

disk head

A

mechanism to read or write data

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13
Q

disk arm

A

moves to position a head on a desired track of the platter

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14
Q

track

A

circular path on surface of disk

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15
Q

block size

A

unit of read or write (aka page)

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16
Q

sectors

A

a part of the track

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17
Q

access time equation

A

rotational delay + seek time + transfer time

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18
Q

rotational delay

A

block under head

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19
Q

seek time

A

move head to right radius

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20
Q

transfer time

A

read time

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21
Q

buffer manager

A

responsible for bringing pages from disk to main memory as needed

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22
Q

buffer replacement policies

A

LRU, clock

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23
Q

sequential flooding

A

situation caused by LRU policy and repeated sequential scans

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24
Q

heap file as linked list

A

header page with one path for full pages and another path for pages with free space

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25
Q

heap fie as page directory

A

each entry for a page keeps track of page availability and number of free bytes

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26
Q

index

A

a data structure that organized records of a table to speed up retrieval

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27
Q

search key

A

attribute or combination of attributes used to retrieve the records (the filter)

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28
Q

index entries

A

two forms
- contains record and key
- contains key and pointer to record

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29
Q

primary index

A

if search key contains primary key

30
Q

secondary index

A

if search key contains any other key

31
Q

unique index

A

if search key contains a candidate key

32
Q

composite search index

A

search on a combination of attributes
- order matters!!

33
Q

clustered index

A

the order of record matches order of index entries

34
Q

unclustered index

A

unordered records
- increases I/Os

35
Q

parameters to consider when creating index

A
  • access time (equality, range)
  • time to access, insert, delete
  • space
36
Q

hash index

A

collection of buckets where each bucket contains one or more index entries

37
Q

bucket

A

primary page + overflow pages

38
Q

static hashing

A

fixed number of buckets

39
Q

problems with static hashing

A
  • cannot grow for more space
  • potentially wasted space if there are long overflow chains
40
Q

extendible hashing

A
  • dynamic hashing
  • keeps a directory of pointers to buckets
  • on overflow, directory is reorganized by doubling the size of it
41
Q

duplicate keys

A

many index entries with same key value

42
Q

Solving for duplicate keys

A
  1. all entries with a given key are on a single page or overflow page
  2. allow duplicate keys in data entries and modify search operation
43
Q

bitmap index

A

store values in multiple tables
- good for duplication and low cardinality

44
Q

bitslice index

A

store value in binary into a single table
- good for high cardinality

45
Q

run

A

a subfile that is sorted

46
Q

pass

A

each time two runs are merged

47
Q

ACID properties

A
  • atomicity
  • consistency
  • isolation
  • durability
48
Q

transactions

A

a collection of operations that create a single atomic logical unit

49
Q

atomicity

A

all actions in the TXN happen, or none happen
- either commit or abort

50
Q

consistency

A

a database in a consistent state will remain in a consistent state after the TXN

51
Q

isolation

A

the execution of one TXN is isolated from other (possibly interleaved) TXNs
- if T1, T2 are interleaved, the result should be the same as T1 then T2 or T2 then T1

52
Q

durability

A

once a TXN commits, its effects must persist
- have to write to disk

53
Q

log

A

a list of modifications
- keeps track of what TXNs change
- stores new and old values of TXNs
- only keeps track of writes
<TXNID, location, old-data, new-data>

54
Q

Write-Ahead Logging (WAL)

A
  1. force log record for an update to disk before page goes to disk (atomicity)
  2. write to disk all log records for a TXN before commit (durability)
55
Q

serial schedule

A

no interleaving

56
Q

serializable schedule

A

a interleaved schedule that is equivalent to some serial schedule

57
Q

serializable schedule

A

an interleaved schedule that is equivalent to some serial schedule

58
Q

equivalent schedule

A

when two schedules will have the same effect for every database state

59
Q

conflict

A

when two different TXMs access the same variable and one of the TXNs is a write

60
Q

anomalies

A

instances where isolation and/or consistency is broken because of a bad schedule

61
Q

types of anomalies

A
  • dirty read
  • unrepeatable read
  • overwriting uncommitted data
62
Q

dirty read

A

when a TXN reads modified data not yet commited
- occurs because of a write, read conflict

63
Q

dirty read

A

when a TXN reads modified data not yet committed
- occurs because of a write, read conflict

64
Q

unrepeatable read

A

when data is read twice but in between the reads, the data was modified
- occurs because of a read, write conflict

65
Q

overwriting uncommitted data

A

when a TXN overwrites the data of an uncommitted TXN
- occurs because of a write, write conflict

66
Q

conflict equivalent

A

when two schedules have the same actions of the same TXNs and conflicting actions are ordered in the same way

67
Q

conflict serializable

A

when a schedule is conflict equivalent to a serial schedule

68
Q

locking

A

used for concurrency control

69
Q

shared mode (S lock)

A

when a TXN wants to read, and another transaction also wants to read

70
Q

exclusive mode (X lock)

A

no other TXN can read or write

71
Q

Strict 2 Phase Locking

A

Lock procedure that maintains isolation and consistency
- each TXN must obtain an S lock before reading and a X lock before writing
- if there is an X lock, no other TXN can get a lock
- all locks are released when TXN completes

72
Q

Deadlock

A

when all transactions are waiting for a lock to be released

CS 564 (2 decks)

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