SMU ASSIGNMENT OF MCA 3RD SAM ASSIGNMENT OF ADVANCED DATABASE MANAGEMEN SYSTEM

   ASSIGNMENT OF ADVANCED DATABASE MANAGEMEN SYSTEM

Question No 1. Describe the following: a) Hierarchical Model b) Network Model

Hierarchical data model:- Here we organize data into a structure which appears as a tree. In this stricter, every node comprises one parent nod. Root node is an exception, that is, it does not contain any parent. This is to note the although a node can comprise numerous child nodes, but it can comprise just one parent node. A record is represented by a node available in structure which appears as tree.

Advantages

Simplicity:- it has simple design process since data in many practical circumstances usually consists of hierarchical relationship. It is thus easier to see the data organized in this manner.

Security:- These databases can execute the changing level of security characteristics.

Database Integrity:- it is extremely advertised in these systems due to its inbuilt structure of parent and child.

Relationship handling:- these database are considered as extremely proficient for the relationships of the type 1:M.

Network Model:-

This model was invented by Charles Bachman afterwards by means of  CODASYL conference on data systems languages association in 1969. It was formulated into a standard arrangement. This model is considered similar to the hierarchical model. However this model permits every record to comprise numerous records of parent as wll as child thus generating a network structure.

Some network databases examples that are most commonly used are:

Turbo IMAGE

IDMS
RDM Embedded

RDM Server

Advantages of network model:

Simplicity: This model is easy to design because mostly all instances of data relationship usually occur as N:M type.

Relationship handling: It is proficient of handling relationship in a better manner the relationship of the type N:M can accommodate various complicated relationships tha are available in real is provided.

Flexibility: These databases provide more flexibility as compared to hirarachical database. This is because here you can navigate data items in numerous ways. Thus high level of flexibility of data access is provided.

Standards: These databases include the development of worldwide standards.

Question No 2. Explain the physical query plan operators. What is the significance of Iterators?

 Logical Operators 

Some information in this topic is preview and subject to change in future releases. Preview information describes new features or changes to existing features in Microsoft SQL Server 2016 Community Technology Preview 2 (CTP2).

Operators describe how SQL Server executes a query or a Data Manipulation Language (DML) statement. The query optimizer uses operators to build a query plan to create the result specified in the query, or to perform the operation specified in the DML statement. The query plan is a tree consisting of physical operators. You can view the query plan by using the SET SHOWPLAN statements, the graphical execution plan options in SQL Server Management Studio, or the SQL Server Profiler Showplan event classes.

Operators are classified as logical and physical operators.

Logical operators describe the relational algebraic operation used to process a statement. In other words, logical operators describe conceptually what operation needs to be performed.

Physical Operators

Physical operators implement the operation described by logical operators. Each physical operator is an object or routine that performs an operation. For example, some physical operators access columns or rows from a table, index or view. Other physical operators perform other operations such as calculations, aggregations, data integrity checks or joins. Physical operators have costs associated with them.

The physical operators initialize, collect data, and close. Specifically, the physical operator can answer the following three method calls:

Init(): The Init() method causes a physical operator to initialize itself and set up any required data structures. The physical operator may receive many Init() calls, though typically a physical operator receives only one.

GetNext(): The GetNext() method causes a physical operator to get the first, or subsequent row of data. The physical operator may receive zero or many GetNext() calls.

Close(): The Close() method causes a physical operator to perform some clean-up operations and shut itself down. A physical operator only receives one Close() call.

The query optimizer creates a query plan as a tree consisting of logical operators. After the query optimizer creates the plan, the query optimizer chooses the most efficient physical operator for each logical operator. The query optimizer uses a cost-based approach to determine which physical operator will implement a logical operator.

Usually, a logical operation can be implemented by multiple physical operators. However, in rare cases, a physical operator can implement multiple logical operations as well.

Question No 3. Differentiate between Serialisability and Recoverability.

Serializability:-

Serializability is the classical concurrency scheme. This helps to ensures that a schedule with regard to performing executing concurrent transactions is equivalent to one that executes the transactions serially in some order. It assumes that all accesses towards the database are done using read and write operations. A schedule is known as correct if we can find a serial schedule that is equivalent to it.

Two major types of serializability exist: view-serializability, and conflict-serializability. View-serializability matches the general definition of serializability given above. Conflict-serializability is a broad special case, i.e., any schedule that is conflict-serializable is also view-serializable, but not necessarily the opposite. Conflict-serializability is widely utilized because it is easier to determine and covers a substantial portion of the view-serializable schedules. Determining view-serializability of a schedule is an NP-complete problem (a class of problems with only difficult-to-compute, excessively time-consuming known solutions).

View-serializability of a schedule is defined by equivalence to a serial schedule (no overlapping transactions) with the same transactions, such that respective transactions in the two schedules read and write the same data values ("view" the same data values).

Conflict-serializability is defined by equivalence to a serial schedule (no overlapping transactions) with the same transactions, such that both schedules have the same sets of respective chronologically ordered pairs of conflicting operations (same precedence relations of respective conflicting operations)

Recoverability:-

Serializability recognizes schedules which preserve database consistency, assuming no transaction fails. Could also examine recoverability of transaction within schedules. If transaction fails, atomicity requires effect of transaction to be undone. Durability states that once transaction commits, its change cannot be undone (without running another, compensating, transaction).

Serializability of a schedule means equivalence (in the outcome, the database state, data values) to a serial schedule (i.e., sequential with no transaction overlap in time) with the same transactions. It is the major criterion for the correctness of concurrent transactions' schedule, and thus supported in all general purpose database systems.

The rationale behind serializability is the following:

If each transaction is correct by itself, i.e., meets certain integrity conditions, then a schedule that comprises any serial execution of these transactions is correct (its transactions still meet their conditions): "Serial" means that transactions do not overlap in time and cannot interfere with each other, i.e, complete isolation between each other exists. Any order of the transactions is legitimate, if no dependencies among them exist, which is assumed (see comment below). As a result, a schedule that comprises any execution (not necessarily serial) that is equivalent (in its outcome) to any serial execution of these transactions, is correct

Question No 4. Discuss about Parallel query processing. How parallel-execution works?

Parallel query processing:- In paraleel query processing multiple processes together at the same time to handle one individual SQL statement. The database  server can handle the statement more swiftly in comparison to a single server by segregating the work necessary to process a statement among various multiple servers. The feature helps to dramatically enhance functioning for data inhance operations related with decision-support applications and ever extremely big database environments. Parallel query feature is most useful for SMP (Symmetric multiprocessing) clustered or MPP(massively parallel systems) because of the fact that in such types of systems the query processing could be efficiently split up among various central processing units on one single system. In parallel query processing, the query is parallelized dynamically at the execution time itself. It automatically adapts to optimize itself for parallelization, if the location or distribution of the data changes. How parallel execution works The basic unit of work in parallelism is called a granule. When a database instance starts up, the database makes a pool of parallel-execution servers that are present for any parallel operation. When performing a parallel operation the coordinator acquires parallel-execution servers from the group and allocates them to the operation. The one proces by the name of parallel-execution coordinator assigns execution of one granule to many parallel-execution servers and co-ordinates result from every server processes and return to the user. Parallel-execution is helpful for various types of operations that access considerable amounts of data. Parallelism enhances performance for ·        Queries ·        Formation of  large indexes ·        Volume inserts, updates, and deletes ·        Aggregations and copying  Question No 5. Differentiate between homogeneous and heterogeneous Database.

Homogeneous:-

When the database technology is the same at each of the locations and the data at the several locations are also compalitble that data is known as homogenous database. The following conditions should exist for homogenous database:

·        The operation system used at each of the locations is the same or at least they should be extremely compatible.

·        The data models used at every location should be the same.

·        The database management used at every location should be the same or at least they should be extremely compatible.

·        The data at the different location should have common definitions and formats.

Homogenous database make the sharing of data between the different users simpler. This signifies the design goal for the distributed database. Achieving this objective needs a very high level planning during the planning phase.

Heterogeneous database:

In heterogeneous DDMS every one of the site might manage different types of DBMS wares, which does not need to be established on the similar original data model and so the system should be made of RDMS OODMS & ORDBMS products.

·        In heterogeneous database contact among various DBMS is needed for translations.

·        So as to give DBMS transparency users should be able to make requests in DBMS language at the local  site.

·        Data from other sites might have a variety of hardware, diverse DBMS products and mixture of a variety  of hardware & DBMS products.

·        The job of finding  these data & execution any essential translation are the capabilities of the heterogeneous DDBMS.

Question No 6 Write short notes on ODMG standards. What are the various components of ODMG-93?

ODMG Standard:

A working group composed of five representatives of the OODBMS vendors established ODMG standard. It provides an inclusive framework for designing an object database writing portable applications in C++ or Smalltalk and querying the database with a simple and very powerful query language.

Major Components of ODMG standard:

Object model :

 it is the model on which the fundamental concepts of object-oriented data structures such as classes, objects , encapsulation, inheritance, interfaces, operations, etc.

Object definition language ODL:-

Object definition language defines how to formulate a database schema the structure of a database. It is neutral to programming languages.

Object interchange format:

This determines how the various objects are represented for exchanging them between different OODBMS.

Object query language (OQL)

OQL is the query language for ODMG object model. Thus it is projected to retrieve data from an object base. It is not concerned with keeping it up to data and neither has it explained the SQL like abstractions such views constraints and stored procedures. It is intended to work directly with various programming language for which a requisite is defined such as C++ java or SMALLTALK.

Binding to programming language C++, SMALLTALK and JAVA:

It is the ODMG binding to programming languages like C++ java and Smalltalk.

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Semester      : Third MCA

Name            : Akash Verma

Roll No         : 14002009414