Bt0066 database management system1

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Database Management System
BT0066 Part-1
By Milan K Antony

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 What are the representative applications of
Databases? List them.
A collection of programs that enables you to store, modify,
and extract information from a database. There are many
different types of DBMSs, ranging from small systems that run
on personal computers to huge systems that run on
mainframes. The following are examples of database
applications: computerized library, systems automated teller
machines, flight reservation systems, computerized parts
inventory systems.
Databases function in many applications, spanning virtually
the entire range of computer software. Databases have
become the preferred method of storage for large multi-user
applications, where coordination between many users is needed.
Even individual users find them convenient, and many electronic
mail programs and personal organizers are based on standard
database technology. Software database drivers are available
for most database platforms so that application software can
use a common API to retrieve the information stored in a
database. Commonly used database APIs include JDBC and
ODBC.

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2. Explain Oracle Architecture with a neat diagram.
Oracle Database Server is made of two major
components.Oracle Server = Oracle Instance (RAM) + Oracle
Database (Physical disk)
Oracle Instance
 Created in the RAM of the server.
 Gets created on startup of the database.
 Memory size and other related parameters are defined in
parameter file.
 Used to access the database (Physical files).

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 It is always connected to one database only.
 Made of memory structure and background processes.
When user starts a tool like Oracle forms, other application
software or SQL plus to connect to oracle database, a user
process starts on the user’s machine. It will request the
connection to the database, so server process will start on the
server on which database is created. User process
communicates with Oracle Instance via server process, and
server process communicates with database.
User can create connection with Oracle server by three
different ways:
 1 Tier connection: In this type user log on to the same
machine on which oracle database is resides.
 2 Tire connection: In this type user log on to the
separate client machine and then connects to database
through network. This also called as client-server type of
the connection.
 3 Tier (N Tire) connection: In this type, user log on to
the separate client machine and connect to middle tire-
application server and application server connects to
oracle database.
Session: A session is a separate connection between user and
oracle server. This gets created when user get authenticated
by the oracle server.

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Oracle Database
 It is a physical storage disk on the server.
 It is the physical files related to the database.
 These files are mainly three types.
o Data files - Contains actual data.
o Online Redo log files - Records changes in the data.
o Control files - Contains information to maintain and
operate the database.
 Oracle server also having other files, those are not a part
of database are.
o Password file - Authenticate user to startup and
shutdown the database.
o Parameter file - It defines the characteristics of an
Instance like size of the different memory structure
of the SGA etc.
o Archive log files – These are the offline copies of
the online redo log files.
Click here to get more information about database.
Oracle Instance Details
Oracle Instance = Memory Structure + Background processes.
Memory Structure
It is made of two memory areas:

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 System Global Area (SGA): Created at the startup of
instance.
 Program Global Area (PGA): Created at the startup of
the server process.
System Global Area (SGA):
System Global Area is made of following different memory
areas:
 Database Buffer Cache
 Shared pool
 Redo log buffer
 Large pool (Optional)
 Java pool (Optional)
 Other miscellaneous like area for locks, latches and other
processes related required memory area.
 Differentiate relation and relation schema.
Relational Schema refers to meta-data elements which are
used to describe structures and constraints of data
representing a particular domain. Whereas a relation is a
property or predicate that ranges over more than one
argument. Relation and Relation schema are the terminologies
of SQL and Relation is known as Table and Relation Schema is
known as Table definition. In other words, Relation schema
defines the meta data elements which represent a particular
domain. For example, they define the structures and
constraints of data. On the other hand, relation is the

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predicate for example, Relation schema for a person "relation"
can be shown in the following manner:
Person(FirstName, LastName, Age, Gender, Address)
A relation schema can be thought of as the basic information
describinga table or relation. This includes a set of column
names, the data types associatedwith each column, and the
name associated with the entire table
A database relation is a predefined row/column format for
storing information in a relational database. Relations are
equivalent to tables.
 Explain indexed and virtual storage access methods.
ISAM (Indexed Sequential Access Method), like physical
sequential files, stores the records back-to-back, making for
very efficient use of disk space. However, unlike physical
sequential, ISAM files must be stored on disk, since the disk
addresses are needed to create the indexes. The physical
location of records within ISAM is not important since the
indexes take care of the access to the records. A single
ISAM file may have many dozens of indexes, each allowing the
files to be retrieved in some pre-defined order. In some
case, the size of the indexes will exceed the size of the base
file. the Virtual Storage Access Method (VSAM) (Virtual
Storage Access Method) it is a combination of the best
features of QSAM and ISAM. Allows physical sequential files to
be indexed on multiple data items. By having multiple indexes,
data can be retrieved directly in several ways and you can

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access data anywhere in the file using a different index. VSAM
is designed specifically for use with disks. Because VSAM data
set structure permits the use of both direct and sequential
access types, you can select either the type or the combination
of access types that best suits your specific application
requirements.
5. What information is stored in the system catalogs?
The system catalog is a collection of tables and views
that contain data about the following:
 Tables and views in a DBEnvironment
 Any indexes, hash structures, constraints, and rules
defined for tables
 DBEFiles and DBEFileSets in the DBEnvironment
 Specific authorities granted to each user
 Programs that can access data in the DBEnvironment
 Current DBEnvironment statistics
 Temporary space for sorts
 Procedures
ALLBASE/SQL uses the system catalog to maintain data
integrity and to optimize data access. The system views are
primarily a tool for the DBA. Initially, only the DBA can

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access these views. Other users need to be granted SELECT
authority by the DBA to access them. Users without SELECT
authority can retrieve descriptions of database objects they
own from the CATALOG views. For information on system and
catalog views, refer to chapter "System Catalog" in the
ALLBASE/SQL Database Administration Guide.
When a DBEnvironment is first configured, the information in
the system catalog describes the system tables and views
themselves. As database objects are defined, their definitions
are stored in the system catalog. As database activities occur,
most of the information in the catalog is updated
automatically, so the system catalog provides an up-to-date
source of information on a DBEnvironment.
Immediately following an UPDATE STATISTICS statement, the
views in the system catalog, summarized in Table 2-2, are a
source of up-to-date information on a DBEnvironment and
the structure and use of its databases. Refer to the
ALLBASE/SQL Database Administration Guide for additional
information on the system catalog.
6. What are entities and attributes? Give examples.
Entity,Object in the real world.Attributes,Describe each
entity. the entity is typically a Clinical Event, as described
above. In more general-purpose settings, the entity is a
foreign key into an "Objects" table that records common

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information about every "object" (thing) in the database – at
the minimum, a preferred name and brief description, as well
as the category/class of entity to which it belongs. Every
record (object) in this table is assigned a machine-generated
Object ID.
As you begin to design the music database, you are either
creating a new system or you are transferring data from a
non-relational system to ALLBASE/SQL. Regardless of where
you're coming from, you need to take a comprehensive look at
all the information needs that will be served by the database
system. This means identifying the elements for which you need
to store and retrieve information. These elements are known
as entities. A list of entities grows out of studying how the
data is used by its owners.
By approaching the problem intuitively, you can probably
identify four different categories of information required by
the radio station:
 Album information.
 Selection information.
 Composer information.
 Station log information.
These are the entities in the data.

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Next, you need to define the attributes of each entity, which
are the useful pieces of information to be stored in tables.
In addition to supplying informational detail, some attributes
are used to distinguish one entity from another. As you
subdivide your data, make sure that for each entity you
define, at least one attribute can uniquely identify an instance
of the entity. This attribute or group of attributes is known
as a key.
Table 2-1 Attributes for Four Entities
Album Entity
Selection
Entity
Composer
Entity
Station Log
Entity
Album Name
Selection
Title
Name
Selection
Title
Medium
Composer
Name
Date of
Birth
Start Time
Album Cost Timing Birthplace End Time
Recording
Company
Performers Comment Announcer
Date
Recorded
Comment Comment
Manufacturer'
s Code
Comment

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As the design evolves, entities eventually become database
tables, and attributes eventually become columns. Note,
however, that at this stage you have not yet identified the
form of the database tables. Before you can do that, you
need to identify relationships.
7. List and explain MySQL architectural primary subsystems.
MySQL is based on a tiered architecture, consisting of both
primary subsystems and support components that interact with
each other to read, parse, and execute queries, and to cache
and return query results.
Primary Subsystems
The MySQL architecture consists of five primary subsystems that
work together to respond to a request made to the MySQL
database server:
The Query Engine
The Storage Manager
The Buffer Manager
The Transaction Manager
The Recovery Manager
The organization of these features is shown in Figure 1.We’ll
explain each one briefly to help you gain a better
understanding of how the parts fit together.

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FIGURE 1 MySQL subsystems
The Query Engine
This subsystem contains three interrelated components:
The Syntax Parser
The Query Optimizer
The Execution Component
The Syntax Parser decomposes the SQL commands it receives
from calling programs into a form that can be understood by
the MySQL engine. The objects that will be used are
identified, along with the correctness of the syntax. The
Syntax Parser also checks the objects being referenced to
ensure that the privilege level of the calling program allows it
to use them.
The Query Optimizer then streamlines the syntax for use by the
Execution Component, which then prepares the most efficient
plan of query execution. The Query Optimizer checks to see
which index should be used to retrieve the data as quickly and
efficiently as possible. It chooses one from among the several
ways it has found to execute the query and then creates a
plan of execution that can be understood by the Execution
Component.

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The Query Optimizer uses probability-based induction, so you
may want to override it if you think that you already know the
ideal way to access your query results; this will prevent the
engine from using another, less optimal plan. MySQL provides
you the option of giving the engine certain “hints” if you want
it to use specific indexes without checking the Optimizer.
The Execution Component then interprets the execution plan
and, based on the information it has received, makes requests
of the other components to retrieve the records.
8. Construct an E-R diagram for a car insurance company
whose customers own one or more cars each. Each car has
associated with it zero to any number of recorded
accidents.
The relation between Customers and Cars is 1->n, as one
customer can own one or more cars.
The relation ship between Car-Insurance Company and
Customer can be n->1, as some customers has more than 1
car..so they may have more than one insurance with the
company.
The relationship between cars and Accidents is (0...1) -> n.
(0..1) means it is either 0 or 1.

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9. Explain various performance measures of disks.
The main measures of the qualities of a disk are
capacity, access time, data transfer rate, and reliability,
access time: the time from when a read or write request is
issued to when data transfer begins. To access data on a
given sector of a disk, the arm first must move so that it is
positioned over the correct track, and then must wait for the
sector to appear under it as the disk rotates. The time for
repositioning the arm is called seek time, and it increases with
the distance the arm must move. Typical seek time range from
2 to 30 milliseconds.

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Average seek time is the average of the seek time, measured
over a sequence of (uniformly distributed) random requests,
and it is about one third of the worst-case seek time.
Once the seek has occurred, the time spent waiting for the
sector to be accesses to appear under the head is called
rotational latency time. Average rotational latency time is
about half of the time for a full rotation of the disk.
(Typical rotational speeds of disks ranges from 60 to 120
rotations per second).
The access time is then the sum of the seek time and the
latency and ranges from 10 to 40 milli-sec.
data transfer rate, the rate at which data can be retrieved
from or stored to the disk. Current disk systems support
transfer rate from 1 to 5 megabytes per second.
reliability, measured by the mean time to failure. The typical
mean time to failure of disks today ranges from 30,000 to
800,000 hours (about 3.4 to 91 years).
10. What are the benefits of making the system catalogs
relations?

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The system catalogs are the place where a relational
database management system stores schema metadata, such as
information about tables and columns, and internal bookkeeping
information .To keep track of all objects, their relationships,
etc., the RDBMS use the same technique they are advocating —
a set of relational tables and views. This approach was first
defined in the SQL92 standard (ISO/IEC 9075-2:199x) and was
implemented across all major RDBMS — to a certain degree.
All metadata is made available as catalog views.Catalog
views present metadata in a format that is independent of any
catalog table implementation, therefore catalog views are not
affected by changes in the underlying catalog tables.Catalog
views are the most efficient way to access core server
metadata.Catalog views are the general interface to catalog
metadata and provide the most direct way to obtain,
transform, and present customized forms of this
metadata.Catalog view names and the names of their columns
are descriptive. Query results match what might be expected
by a user who has a moderate knowledge of the feature that
corresponds to the metadata that is being queried.hence all
this help for query optimization.

Bt0066 database management system1

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