1What is a DBMS?
a collection of files that store data and a program that accesses and updates those files
2What is an RDBMS?
a relational database management system
3What drives changes in databases?
data variety and volume leading to big data
4Where are RDBMS commonly used?
backend for applications websites and web services
5What is a two tier database system?
a system with a front end application and a back end database server
6What are the two components of SQL?
data definition language ddl and data manipulation language dml
7What does ddl do?
creates and defines tables
8What does dml do?
inserts updates and queries data
9What is data independence?
separating logical view from physical implementation
10What does the dbms hide from the user?
file creation catalog updates index creation and constraint checking
11What is a declarative query?
a query that specifies what to do not how to do it
12What does the optimizer do?
chooses the best execution plan for a query
13What is an index used for?
to quickly find records without scanning all data
14What happens when a table changes with an index?
the index must also be updated
15What is a transaction?
a sequence of statements that all succeed or all fail
16What are the ACID properties?
atomicity consistency isolation durability
17What is atomicity?
all operations succeed or none do
18What is isolation?
transactions do not interfere with each other
19Why does a dbms control data instead of the os?
it knows data structure and access patterns better
20What are read and write operations?
read transfers data from disk to memory write transfers data from memory to disk
21Why are disk operations expensive?
they involve high cost i o compared to memory operations
22What is the storage hierarchy?
levels from cpu cache and memory to disk and network storage
23What is faster in storage hierarchy?
cache and main memory
24What is slower but cheaper storage?
disk and network storage
25What is sequential io?
reading or writing consecutive blocks on disk
26What is random io?
reading or writing blocks in different locations requiring multiple seeks
27Which is faster sequential or random io?
sequential io
28What is disk latency?
time to access data including seek rotation and transfer
29What are components of disk delay?
seek time and rotational latency
30What is seek time?
time to move disk head to the correct track
31What is rotational latency?
time waiting for the disk to rotate to the correct sector
32What is transfer time?
time to actually read or write data
33What is average rotational latency?
half the time of one full disk rotation
34What is the key to reducing disk io cost?
reduce seek time and rotational latency
35What is striping?
using multiple disks to increase access speed
36What is mirroring?
duplicating data across disks for reliability and faster reads
37What is disk scheduling?
ordering disk requests to improve performance
38What is the scan algorithm?
moves the disk head in one direction serving requests then reverses
39What is prefetching?
loading data into memory before it is requested
40What is buffering?
temporarily storing data in memory to reduce disk access