Database Administration, Database Administration, Integrity and PerformanceIntegrity and Performance

ObjectivesObjectives

Define the roles of database Define the roles of database administratoradministrator

Describe the term integrityDescribe the term integrity Define the term securityDefine the term security Define the basic performance Define the basic performance

measuresmeasures

The Database AdministratorThe Database Administrator

Data Administrator(DA) makes the Data Administrator(DA) makes the strategies and policies decisions strategies and policies decisions regarding the data of the enterprise.regarding the data of the enterprise.

Database Administrator(DBA) Database Administrator(DBA) implements those decisions implements those decisions technically.technically.

Functions of DBAFunctions of DBA

Creating the conceptual schema Creating the conceptual schema (logical or conceptual database (logical or conceptual database design)design)

Creating the internal schema Creating the internal schema (physical database design)(physical database design)

Functions of DBAFunctions of DBA

Defining security and integrity Defining security and integrity constraintsconstraints

Defining backup and recovery Defining backup and recovery policiespolicies

Monitoring performance and Monitoring performance and responding to changing responding to changing environments.environments.

SECURITYSECURITY

Protecting the data against Protecting the data against unauthorised disclosure, alteration unauthorised disclosure, alteration or destruction.or destruction.

Security is enforced bySecurity is enforced by

DBMS’s security subsystemDBMS’s security subsystem Checking access requests to Checking access requests to

security constraints stored in system security constraints stored in system catalogcatalog

Giving certain privileges in a relation Giving certain privileges in a relation to certain usersto certain users

What are views for?What are views for?

Automatic Security for hidden dataAutomatic Security for hidden data Short hand capabilityShort hand capability Same data to be seen by different users in Same data to be seen by different users in

a different way at the same timea different way at the same time May provide logical data independenceMay provide logical data independence

• immunity of users and user programs to immunity of users and user programs to changes in the logical structure of a databasechanges in the logical structure of a database

• GrowthGrowth– new attributes may be added new attributes may be added – new relations may be added new relations may be added

SQL FACILITIES FOR VIEWSSQL FACILITIES FOR VIEWS

CREATE VIEW < view name> AS <table expression>CREATE VIEW < view name> AS <table expression>

[ WITH [<qualifier>] CHECK OPTION ][ WITH [<qualifier>] CHECK OPTION ]

With check option means that INSERT and With check option means that INSERT and UPDATE on the view will be rejected if UPDATE on the view will be rejected if they violate any integrity constraint they violate any integrity constraint implied by the view defining expressionimplied by the view defining expression

Qualifier is CASCADED { Default } or Qualifier is CASCADED { Default } or LOCALLOCAL

Examples of viewsExamples of views

CREATE VIEW BestsupplierCREATE VIEW Bestsupplier

AS SELECT S.S#, S.STATUS, S.CITY AS SELECT S.S#, S.STATUS, S.CITY

FROM SUPPLIERFROM SUPPLIER

WHERE SUPPLIER.STATUS > 15 WHERE SUPPLIER.STATUS > 15

WITH CHECK OPTIONWITH CHECK OPTION ; ;

Examples of viewsExamples of views

CREATE VIEW GREENPART ASCREATE VIEW GREENPART AS

SELECT PART.P#, PART.NAME,SELECT PART.P#, PART.NAME, PART.WEIGHT AS PART.WEIGHT AS WT, WT,

PART.CITY PART.CITY

FROM PART FROM PART

WHERE PART.Color = ‘Green’WHERE PART.Color = ‘Green’

WITH CHECK OPTION;WITH CHECK OPTION;

Examples of viewsExamples of views

CREATE VIEW HEAVY_GREENPART ASCREATE VIEW HEAVY_GREENPART AS

SELECT GP.P#, GP.NAME, GP.WT, SELECT GP.P#, GP.NAME, GP.WT, GP.CITY GP.CITY

FROM GREENPART AS GPFROM GREENPART AS GP

WHERE GP.WT > 12.0WHERE GP.WT > 12.0

WITH CHECK OPTION;WITH CHECK OPTION;

Views and SecurityViews and Security

GRANT SELECT, UPDATE (NAME,WT),GRANT SELECT, UPDATE (NAME,WT),

DELETE ON DELETE ON GREENPARTGREENPART

TO user1, user2;TO user1, user2; Privileges can be USAGE, SELECT, Privileges can be USAGE, SELECT,

INSERT, UPDATE, DELETE and INSERT, UPDATE, DELETE and REFERENCESREFERENCES

Can be provided WITH GRANT OPTIONCan be provided WITH GRANT OPTION

REVOKE REVOKE

REVOKE DELETE ON REVOKE DELETE ON GREENPARTGREENPART FROM FROM user1 RESTRICTuser1 RESTRICT

Revoke can be done for GRANT OPTION Revoke can be done for GRANT OPTION FOR alsoFOR also

RESTRICT is needed if a privilege is RESTRICT is needed if a privilege is granted furthergranted further

What is Integrity?What is Integrity?

Accuracy or correctness of data in a Accuracy or correctness of data in a databasedatabase

Mostly RDBMS provide two kind of Mostly RDBMS provide two kind of Integrity support:Integrity support:• Declarative Integrity supportDeclarative Integrity support• Procedural Integrity supportProcedural Integrity support

Declarative SupportDeclarative Support

In the form of constraint definitionsIn the form of constraint definitions If a new constraint is declared then the If a new constraint is declared then the

system ensures that current state of system ensures that current state of database satisfies it, otherwise, the new database satisfies it, otherwise, the new constraint is rejectedconstraint is rejected

If a DBMS provides declarative support, If a DBMS provides declarative support, then about 90% of typical database then about 90% of typical database definition would consist of constraints.definition would consist of constraints.

Declarative Support Contd..Declarative Support Contd..

A system providing such support A system providing such support relieve application programmers of relieve application programmers of the burden, thus, increases the burden, thus, increases productivityproductivity

Golden RuleGolden Rule

No update operation must ever No update operation must ever be allowed to leave any relation be allowed to leave any relation in a state that violates its own in a state that violates its own predicate. No update transaction predicate. No update transaction must ever be allowed to leave must ever be allowed to leave database in a state that violates database in a state that violates its own predicate. its own predicate.

State Vs Transition State Vs Transition ConstraintsConstraints

Concerned with the correct state Concerned with the correct state of databaseof database

Constraints on legal transitionsConstraints on legal transitions

• Not married to marriedNot married to married

• No student class should ever No student class should ever deceasedecease

FOREIGN KEYS FOREIGN KEYS .

Let R2 be a relation, then a foreign key in Let R2 be a relation, then a foreign key in R2 is a set of attributes of R2, say FK, R2 is a set of attributes of R2, say FK, such that :such that :

• There exists a relation R1 ( R1 & R2 not There exists a relation R1 ( R1 & R2 not necessarily distinct) with a candidate necessarily distinct) with a candidate key CK; andkey CK; and

• For all times, each value of FK in the For all times, each value of FK in the current value of R2 is identical to the current value of R2 is identical to the value of CK in some tuple in the current value of CK in some tuple in the current value of R1.value of R1.

.

Foreign Key contd ...Foreign Key contd ...

Definition requires that every value of Definition requires that every value of given foreign key appears as a value of given foreign key appears as a value of matching candidate key - Converse is not matching candidate key - Converse is not a requirementa requirement

A foreign key is simple or compositeA foreign key is simple or composite

Each attribute of a given foreign key must Each attribute of a given foreign key must have a same name and type as the have a same name and type as the corresponding component of matching corresponding component of matching candidate keycandidate key

Referential IntegrityReferential Integrity

Foreign key is a ReferenceForeign key is a Reference

Matching candidate key tuple is Matching candidate key tuple is ReferencedReferenced

Referential constraint : A value of foreign Referential constraint : A value of foreign key must match the referenced candidate key must match the referenced candidate keykey

Referencing Relation : Have foreign keyReferencing Relation : Have foreign key

Referenced Relation : Have candidate keyReferenced Relation : Have candidate key

Referential DiagramsReferential Diagrams

.

A given relation can be both referenced A given relation can be both referenced and referencing at the same lineand referencing at the same line

R3 R2 R1R3 R2 R1

R1 & R2 are not necessarily distinct R1 & R2 are not necessarily distinct Example : (Employee, Mgr.) Example : (Employee, Mgr.) Self-referencing relation Self-referencing relation

Foreign to candidate key match is the glue Foreign to candidate key match is the glue that holds database togetherthat holds database together

SQL FacilitiesSQL Facilities

A candidate key definitionA candidate key definition

A foreign key definitionA foreign key definition

A check constraint definitionA check constraint definition

We may assign a name to We may assign a name to constraintconstraint

Candidate KeyCandidate Key

UNIQUE (<column name comma list>)UNIQUE (<column name comma list>) OROR

PRIMARY KEY (<column name comma PRIMARY KEY (<column name comma list>)list>)

At most one Primary key definitionAt most one Primary key definition

Any number of UNIQUE specificationsAny number of UNIQUE specifications

NOT NULL is by defaultNOT NULL is by default

Foreign Key Foreign Key

FOREIGN KEY (< col name comma list>)FOREIGN KEY (< col name comma list>) References <base table name> References <base table name>

[(< column name comma list>)][(< column name comma list>)] [ ON DELETE < referential action>[ ON DELETE < referential action> ON UPDATE<Referential action>]ON UPDATE<Referential action>]

No action{default} or CASCADE or SET No action{default} or CASCADE or SET DEFAULT or SET NULLDEFAULT or SET NULL

Second Comma list, if foreign key Second Comma list, if foreign key references a candidate key that is not references a candidate key that is not primary key.The foreign to candidate key primary key.The foreign to candidate key matching is done on column position ( left matching is done on column position ( left to right)to right)

Example of constraintsExample of constraints

CREATE TABLE CREATE TABLE SupPart ( S# S# NOT NULL,SupPart ( S# S# NOT NULL,

P# P# NOT NULL,P# P# NOT NULL, QTY QTY NOTNULL,QTY QTY NOTNULL,

PRIMARY KEY( S# , P# ) ,PRIMARY KEY( S# , P# ) ,FOREIGN KEY ( S#) REFERENCES SUPFOREIGN KEY ( S#) REFERENCES SUP

ON DELETE CASCADE,ON DELETE CASCADE, ON UPDATE CASCADE,ON UPDATE CASCADE,

FOREIGN KEY ( P#) REFERENCES PARTFOREIGN KEY ( P#) REFERENCES PART ON DELETE CASCADEON DELETE CASCADE ON UPDATE CASCADE,ON UPDATE CASCADE,

CHECK ( QTY > 0 and QTY < 5000) );CHECK ( QTY > 0 and QTY < 5000) );

TRIGGERED PROCEDURESTRIGGERED PROCEDURES

Procedures invoked automatically on Procedures invoked automatically on occurrence of a specified exception occurrence of a specified exception or a specified interval of timeor a specified interval of time

CASCADE referential action is a CASCADE referential action is a simple example of a triggered simple example of a triggered procedure-declaratively specifiedprocedure-declaratively specified

AssertionsAssertions

General constraintsGeneral constraintsCerate ASSERTION < constraints name >Cerate ASSERTION < constraints name > check ( < conditional expression >);check ( < conditional expression >);DROP ASSERTIONS <Constraint name>;DROP ASSERTIONS <Constraint name>; Assertions are always satisfied by database.Assertions are always satisfied by database. On creation validity of an assertion is On creation validity of an assertion is

checked checked Any change in database may result in Any change in database may result in

checking by an creation =>High overheadschecking by an creation =>High overheads

ExampleExample

The sum of all loans of a branch should be The sum of all loans of a branch should be less than total account balances less than total account balances

Create assertion sum-constraintCreate assertion sum-constraintcheck ( not exists (select * from branchcheck ( not exists (select * from branch where (select sum (amount) from loan where (select sum (amount) from loan where loan.branch-name =where loan.branch-name =

branch.branch-branch.branch-name )name )

>=(select sum (amount) from account>=(select sum (amount) from account where loan .branch-name = where loan .branch-name =

branch.branch-name)))branch.branch-name)))

Deferred CheckingDeferred Checking

SQL constraints can be:SQL constraints can be:• DEFERABLE (Initially Immediate OR initially DEFERABLE (Initially Immediate OR initially

deferrable )deferrable )• NOT DEFERABLE NOT DEFERABLE

SET CONSTRAINT <constraint name> SET CONSTRAINT <constraint name> <option>; statement switches on or off <option>; statement switches on or off the deferrable constraintthe deferrable constraint

Option is IMMEDIATE or DEFERRED Option is IMMEDIATE or DEFERRED

Performance Tuning involvesPerformance Tuning involves

Tuning of hardware resourcesTuning of hardware resources Reducing I/O operationsReducing I/O operations

Reducing Disk AccessesReducing Disk Accesses

Indexing is one major technique Indexing is one major technique used to reduce disk accessesused to reduce disk accesses

Ordered indicesOrdered indices

Based on based on sorted ordering Based on based on sorted ordering of of valuesvalues

Index involve Index involve • Access timeAccess time• Insertion timeInsertion time• Deletion timeDeletion time• Space overheadsSpace overheads

Ordered indicesOrdered indices

Index Structure is associated with a Index Structure is associated with a 'Search Key' 'Search Key' • Primary index- on a sequentially sorted Primary index- on a sequentially sorted

file. (index on primary key- not correct)file. (index on primary key- not correct)• Indices whose search key specifies an Indices whose search key specifies an

order different from the sequential order order different from the sequential order of the file are called secondary or non of the file are called secondary or non clustering indices.clustering indices.

Dense IndexDense Index

An index record/ entry appears for An index record/ entry appears for every search key 'value' in the file & every search key 'value' in the file & a pointer to first data record with that a pointer to first data record with that search key valuesearch key value

Sparse IndexSparse Index

Entry only for some of the values and Entry only for some of the values and a pointer to first value of that type.a pointer to first value of that type.• Take less spaceTake less space• A sparse index with one index entry per A sparse index with one index entry per

block may be a good choice.block may be a good choice.

Multilevel IndicesMultilevel Indices

Are useful when size of index is very Are useful when size of index is very largelarge

Secondary IndicesSecondary Indices

It contains pointers to all recordsIt contains pointers to all records It should not be sparseIt should not be sparse Improve performanceImprove performance Overheads on modification of Overheads on modification of

databasesdatabases Tradeoff : Frequency of Queries Tradeoff : Frequency of Queries

versus Modificationsversus Modifications

B TreeB Tree

Is one of the major method of Is one of the major method of implementing indeximplementing index

B tree adds performance overheads for B tree adds performance overheads for insertion and deletion and adds apace insertion and deletion and adds apace overheads.overheads.

This performance overhead is acceptable This performance overhead is acceptable even for files with high frequency of even for files with high frequency of modification- no cost of reorganization modification- no cost of reorganization