Pemrograman Sistem Basis Data Chapter II Database Sistem (Lanjutan)

In This Chapter You Will Learn Developing DBMS from file and system file. What is beneffit of DBMS ? Describing and storing data in DBMS.

Sejarah Awal Mula Database Manual File. ◦ Secara Manual mengumpulkan beberapa file dan disimpan dalam file kabinet ◦ Dikelompokan ke dalam folder (kumpulan) dengan berdasarkan jenis data ◦ Sistem ini cukup memadai untuk jumlah data yang kecil dengan Sedikit laporan. ◦ Pencarian dan penggunaan data yang tumbuh semakin besar mengakibatkan buang waktu dan tenaga

Sejarah Awal Mula Database Konversi dari manual ke komputer file system ◦ Secara Teknik lebih komplek dan membutuhkan aplikasi yang menunjang ◦ Pencarian dilakukan dengan bantuan aplikasi yang komplek

Evolution of Simple File System Berkembangnya Aplikasi yang menggunakan File system sendiri Setiap individu atau bagian dari perusahaan memiliki sistem file sendiri- sendiri

Kelemahan File System Setiap Laporan / Data yang ingin dikumpulkan membutuhkan programmer yang mengerti benar Struktur data secara fisik Karena masih menggunakan bahasa pemrograman generasi ketiga ( 3GL) Membutuhkan Pengkodean yang komplek untuk mendapatkan data dengan karakteristik tertentu. Membuat program baru setiap kali ingin membuat jenis laporan yang baru. Semakin berkembangnya file membuat program semakin sulit. Redudancy data Anomali data

Database VS File System Masalah yang melekat pada files system mulai hilang menggunakan sistem database File system banyak berceceran dan tidak saling berhubungan Database secara logic berhubungan dan tersimpan dalam satu logic penyimpanan.

DBMS Is software designed to assist in maintaining and utilizing large collection of data.

To understand the need for a DBMS A company has a large collection (say, 500 GB ) of data on employees, departments, products, sales, and so on. This data is accessed concurrently by several employees. Questions about the data must be answered quickly, changes made to the data by different users must be applied consistently, and access to certain parts of the data (e.g., salaries) must be restricted.

We can try to manage the data by storing it in operating system files. But have problems : 1. We probably do not have 500 GB of main memory to hold all the data 2. Even if we have 500 GB of main memory, We have to program some method of identifying all data items. 3. We have to write special programs to answer each question a user may want to ask about the data 4. Operating systems provide only a password mechanism for security. This is not sufficiently flexible to enforce security policies in which different users have permission to access different subsets of the data

Advantages of DBMS Data Independence Efficient Data Access Data Integrity and Security Data Administration Concurrent Access and Crash Recovery Reduced Application Development Time

Data Independence Application programs should not, ideally, be exposed to details of data representation and storage, The DBMS provides an abstract view of the data that hides such details

Efficient Data Access A DBMS utilizes a variety of sophisticated techniques to store and retrieve data efficiently. This feature is especially important if the data is stored on external storage devices

Data Integrity and Security If data is always accessed through the DBMS, the DBMS can enforce integrity constraints. For example, before inserting salary information for an employee, the DBMS can check that the department budget is not exceeded. Also, it can enforce access controls that govern what data is visible to different classes of users.

Data Administration When several users share the data, centralizing the administration of data can offer significant improvements. Experienced professionals who understand the nature of the data being managed, and how different groups of users use it, can be responsible for organizing the data representation to minimize redundancy and for fine-tuning the storage of the data to make retrieval efficient.

Concurrent Access and Crash Recovery A DBMS schedules concurrent accesses to the data in such a manner that users can think of the data as being accessed by only one user at a time. Further, the DBMS protects users from the effects of system failures.

Reduced Application Development Time Clearly, the DBMS supports important functions that are common to many applications accessing data in the DBMS. This, in conjunction with the high-level interface to the data, facilitates quick application development. DBMS applications are also likely to be more robust than similar stand-alone applications because many important tasks are handled by the DBMS (and do not have to be debugged and tested in the application)

Describing and storing data in a DBMS Now….Most database management system are based on ther relational data model such as IBM's DB2, Informix, Oracle, Sybase, Microsoft's Access, FoxBase, Paradox, Tandem, and Teradata, etc.

Before learn about relational database…. We should know about Level abstraction in a DBMS…

Level abstraction in a DBMS

continues Next Week… continues Next Week… Thanks for today…. Quis…. What is the different between System File and DBMS ??