Database Design

preliminary

In this paper will discuss the stages in the design database. On the database that is used by a single user or a few users only, the database design is not difficult.

But if the size of the database that is medium or large database design will be very complex. Therefore, users expect the use of a database such that the system must be able to meet the needs of all the users. Of course, that these needs can be served well then it should be done anyway good database design, activities, what is being done at that stage.

Database Design goals

To meet the information comprising user needs specifically and applications - applications.

Facilitate understanding of the structure of information.

Supporting the needs of processing and some objects appearance (response time, processing time, and storeage space).

Database Design Process

Database design process consists of six stages:

Phase 1 Data collection and analysis

Phase 2, the database design is conceptually

Phase 3, Election DBMS

Stage 4, logical database design (model data mapping)

Stage 5, the physical design of the database

Stage 6 Database System Implementation

In particular the design process contains two parallel activities:

Activities that involve the design of the data content and structure of the database,

Activity on the design database processing and applications software.

On the other hand, we usually determine the design of database applications with led to the construction of a database schema that has been determined for the first activity.

6 steps above was not to be processed sequentially. In the phase 1 is a collection of information related to the use of the database. Stage 6 is implementing its database.

Stage 1 and 6 sometimes is not part of the design database. While that is the core of the database design process is at the stage of 2, 4, 5.

Phase 1 - Data collection and analysis

It is a stage where we make the process of identification and analysis needs and data is called data collection and analysis. To determine the needs of a database system, we need to know in advance the other parts of the information system that will interact with the database system, including existing users and the new useryang and their applications. The needs of users and applications is then collected and analyzed.

The following are the activities of data collection and analysis:

Define groups of users and fields of application

A review of existing documentation

Analysis of the operating environment and data processing

The list of questions and interview

Phase 2, the database design is conceptually

At this stage will be generated conceptual schema for the database that depend on a specific DBMS. Often using a high-level of data modelseperti ER / EER modelselama this stage. In the conceptual schema, we must specify databaseyang known applications and transactions mungkin.Tahap databasesecara conceptual design has two parallel activities:

Designing a conceptual scheme

Examine the needs of data from a database that is the result of phase 1 and produce a conceptual database schema in a DBMS-independent high-level data model as EER (Enhanced Entity Relationship) model.Untuk produce such schemes can be generated by merging various user needs and directly create the database schema or by designing schemes apart from the needs of each user and then combining these schemes. The data model used in the design of conceptual scheme is DBMS-independent and the next step is to choose a DBMS to do the design.

Designing transactions

Testing applications databasedimana her needs have been analyzed in phase 1, and generating details of transactions ini.Kegunaan this stage are processed in parallel along tahapp conceptual schema design is to design the characteristics of database transactions that have been known at a DBMS- independent. These transactions will be used to process and manipulate databases such time as the database is implemented.

Phase 3, Election DBMS

Selection databaseditentukan by several factors, including factors engineering, economics, and politics organisasi.Contoh technical factors:

The existence of DBMS in performing its duties as the types DBMS (relational, network, hierarchical, etc.), storage structures and access points that support DBMS, users, and others-lain.Faktor-economic and organizational factors that affect each Another in the selection of DBMS:

Data Structure

If the data stored in the database following the hierarchical structure, it is a kind of hierarchy of the DBMS should be considered.

Personal who has been accustomed to a system

If the programmer staff in an organization are familiar with a DBMS, then this can reduce training costs and time to learn.

Availability of the service seller

The existence of the seller service facilities are needed to help solve some of the problems of the system.

Stage 4, logical database design (model data mapping)

The next stage is to create a conceptual schema and the external schemas in the data model of the DBMS chosen. This phase is done by mapping the conceptual schema and the external schemas generated in stage 2. At this stage, the conceptual schema is transformed from high-level data model used in phase 2 into the data model of the data model of the DBMS chosen at this stage of the 3.Pemetaan can be processed in two levels:

Mapping system-independent

Mapping to the DBMS data model without considering the characteristics or special things that apply to the DBMS implementation of the data model.

Adjusting the scheme to the specific DBMS

Set the schema generated in step 1 to be adapted to the specific implementation in the future of a data model used on the DBMS dipilih.Hasil of this stage wearing commands DDL (Data Definition Language) language chosen DBMS that determines level of conceptual and external schema of the database system. But 10 in some cases, DDL commands to enter parameters so that the physical design of a complete DDL had to wait until the design phase has been lengkap.Tahap physical databasesecara can be started after the election of an implementation data model while waiting specific DBMS will be selected. Example: if it decides to use some relational DBMS, but has yet to decide a primary relationship. The design of the external schemas for specific applications can often be completed during this process.

Stage 5, the physical design of the database

Physical database design is the process of selecting the storage structures and access paths to the files database for achieving the best performances in various aplikasi.Selama this phase, designed the specifications for the database stored associated with storage structures physical, placement record and access points. Related to the internal schema (the term 3-level architecture of DBMS) .Some guidance in selecting the design of the physical databasesecara:

Response time

The elapsed time of a transaction database that is proposed to carry out a response. The main influence on the response time is under the supervision of the DBMS are: database access time to a data item designated by a transaction. Response time is also affected by several factors that are not under the supervision of the DBMS, such as scheduling the operating system or communication delays.

Space utility

The amount of storage space used by the database files and structures the access point.

Transaction throughput

The average number of transactions that can be processed per minute by the system database, and the critical parameters of the transaction system (eg used at booking a place on the plane, banks, etc.). Results of this phase is penentual beginning of the storage structure and access to database files.

Stage 6 Database System Implementation

Once the design is logically and physically complete, we can implement a database system. DDL commands in and SDL (Storage Definition Language) of the DBMS selected, collected and used to create the database schema and database files (which is empty). Now databasetersebut loaded (together) with datanya.Jika data must be changed from the previous computer system, changes in routine may be required to re-format the data that is then inserted into the new database. Transactions database should now be implemented by the programmmer aplikasi.Spesifikasi conceptually tested and linked to the program code with the commands of the embedded DML has been written and tested. One moment of such transactions has been prepared and the data has been entered into the database, the design and implementation phase has been completed, and then the operational phase of the database system begins.

Closing

So in designing the database there are 6 stages. In the design of this database is important to do as well as possible in order to produce a good system.