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Practical DBMS > DBMS Intro > Flashcards

DBMS Intro Flashcards

1
Q

What is a Database

A

Collection of structured data stored on persistent storage

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2
Q

Environmental and Contextual

A
  • Available toa large amount of end users (No delay/Access Denial/Loss of data)
  • Correctness of computations and upholding assertions (Get right value until its changed)
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3
Q

General Purpose DBMS

A

Computer based application toolset to define, create , control and manage DB/Users/Perms/Admins.

It demands flexibility + generality in terms of allocation of computer resources and storage space.

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4
Q

Requirements of General Purpose DBMS

A
  • Reliability (resilience to faults and interruptions)
  • Openness (data connectivity)
  • Scalability (Storage and throughput)
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5
Q

Each storage device differs in

A

Capacity, Mode of Access, Speed, Bandwidth, Reliability, Volatility, Cost.

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6
Q

Three Important DBMS Functionalities

A
  • Query Processing
  • Transaction Management
  • Storage Management
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7
Q

Any functionality must address these two areas of concern

A
  • Consistency (returns some result under invariant states)
  • Efficiency (Computational time and space of DBMS activities)
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8
Q

Storage Management

A

Data file per table structure, heap, basic (tree type) indexing, basic (hash based) indexing, Some DBMS structure their data files as a paged heap (Cache).

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9
Q

Query Processor

A

Process that transforms or executes a user-defined query against a database state and returns those instances that satisfy the query.

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10
Q

Declarative Query

A

Data access expression that indicates the structure and the property of the result (i.e What you want).

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11
Q

Procedural Query

A

Specifies structure, property and an exact computational program

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12
Q

Query Optimization

A

Tuning of queries and storage structures to favor the performance of some frequently used queries.

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13
Q

Data Access Path

A

Procedure to traverse and access required data items through the use of available look up methods associated to the data file organization

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14
Q

Relational Algebra Fundamental Operators

A
  • Unary SELECT (Restriction with a predicate)
  • Unary Project (list of attributes)
  • Binary Union (of two relations)
  • Binary set difference
  • Binary product
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15
Q

Examples of other operators that can be defined from the RA fundamental operators

A

JOIN, INTERSECT, DIVISION

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16
Q

Each Relation Algebra has its own math properties such as:

A

Commutativity, associativity, distributivity, monocity

These properties allow us to express a query construct with a multiple of mathematically equivalent expressions.

Different expressions that are equivalent yield the same output but process differently.

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17
Q

Relational Algebra uses

A
  • Useful in QP and QO of declarative languages
  • Applicable for parallel implementations

RA needs to be augmented with a number of other operations

18
Q

Partition/Frame

A

Section of table (can be used in RA to return a row)

19
Q

Transaction Modelling

A

Unrestricted sharing over data is problematic (ex. Dirty Read)
An explicit sequence of data manipulation commands over a DB are abstracted as a single logical update i.e transaction.

20
Q

When is a transaction valid?

A

If all its subparts have succeeded

21
Q

What can a valid transaction do?

A

Can commit, otherwise will have to rollback

22
Q

Transaction modelling complicates

A

the scenario when allowing data sharing. DBMS typically insulates this from users

23
Q

Transaction’s ACID properties

A

Atomicity (Data executes completely or not at all)
Consistency (Transaction preserves internal consistency of DB)
Isolation (Transaction executes as if it were running alone, with no other transactions)
Durability (Transactions result will not be lost in the future)

24
Q

Specialized DBMS

A

Great for caching, load balancing, streaming or queueing semantic work, distributing data and code.
But not general purpose DBMS, buyer must be responsible for knowing what they need before purchasing.

ACID/CUASAL?BASE, data modelling, query language…

25
Q

Persistence of Data

A

Present in Specialized DBMS

High level of physical data independence, Aid development of computer information system, Reliable and Efficient.

Storage manager should efficiently come with query and transaction processing. Query Processing should come with transaction processing.

26
Q

Specialized DBMS Constraint

A
  • Fit for purpose
  • Query + Data Modelling
  • Storage planning and allocation
  • Transaction processing
27
Q

Operational Goals

A

Tune CIS’s data access requirements (Tuning levelled at DBMS). Establish performance expectations and limits for CIS, even by testing and ensure configuration meets these. Learn + Teach principles and goals to SD team including DBA hosting.

28
Q

Database Lifecycle (Physical Part)

A

When DBMS specific artefacts are introduced, one can introduce physical objects to address performance, reliability and connectivity issues. These artefacts can be hardware, indexes, data placement policies or DBMS set-up parameters.

29
Q

Once DB is active (in Lifecycle)…

A

DBMS tools are used for monitoring performance and comparing with guidelines

30
Q

Guiding Principles

A
  • If table is not 3NF, decompose it
  • Data redundancy at conceptual level is the need to ensure that data in a DB is not duplicated, If duplication exists then inconsistency arising from it must be addressed.
  • We want to minimize data redundancy at logical level
31
Q

With data independence, what can we do w.r.t artefact

A

We can make changes to the artefact without having to remap all the higher artefacts. Separation of physical data items (files), logical data items (rDB) and app programs that interact with database minimizes their interdependence.

32
Q

Logical Data Independence

A

Changes to schema do not necessitate changes in application programs ex. adding new data-types.

33
Q

Physical Data Independence

A

Changes to physical schema are insulated from conceptual and application programs that use database ex. re-structuring index

34
Q

Classic DB representation

A

ANSI/SPARC

35
Q

3 Levels of abstraction

A
  • Internal Schema
  • Conceptual Schema
  • External Schema
36
Q

Internal Schema

A

Physical storage model containing info such as devices, file locations, structures

37
Q

Conceptual Schema

A

A single and consistent model of the DB of interest

38
Q

External Schema

A

A view of the conceptual mode applicable users or processes. Usually many of these and view overlapping is allowed.

39
Q

Minimize disruption due to schema

A
  • Change to physical schema characteristics without the need to change the conceptual schema.
  • Change the external views without changing the conceptual schema
40
Q

Data security

A

Data is indispensable, protect it from abuse such as security breaches, errors, contention, hard disk failures etc.

Practical DBMS (9 decks)

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