Database Design Advantages And Disadvantages

(a) The major advantages of a database system approach to managing data include improving data sharing for users, improving data security, improving data access and improving data integration while minimizing data inconsistencies. This will lead to improved decision making and productivity. The major disadvantages of a database system approach to managing data include increased costs both initial set-up and ongoing maintenance, management complexity, managing the discipline and procedures to maintain concurrency and the potential to be locked in to a specific vendor and incurring high upgrade and replacement costs frequently.

(b) There are six (6) phases in the DBLC methodology to design and implement a database system. These phases are as

The Database Design: In this phase the focus is on the design of the database model.

3. The Database Implementation and Loading: In this phase the database is built which involves installing the DBMS, creating the tables and loading data.

4. Testing and Evaluation: In this phase the designed databases functionality is tested, fine-tuned and evaluated.

5. Operation: In this phase the database has completed its design process and is considered operational, at this stage the process of evolution is considered to have begun.

6. Maintenance and Evolution: In this phase the database administrator begins his or her work, assigning access rights to users, performing system maintenance both predictive and corrective if required. Also as part of the evolution of the system ongoing adaptive maintenance is required to enhance performance and facilitate expansion of the system etc.

(c) The differences between a file-processing system and a DBMS include but are not limited to the following.

1. A file-processing system coordinates physical access to a data set whereas a DMBS coordinates both logical and physical access.

2. Duplication of data is reduced, and consistency is greatly increased by use of a

This comprises the shared pool, the database buffer, and the redo-log buffer. Also, several background processes are started. These combined constitute the database instance. All database operations take place in the SGA. If several users are connected they all share the SGA. Information in the SGA is divided into three caches.

The database buffer is a cache that holds the data blocks that are read from data files. Blocks can contain table data, index data etc.

The Redo-Log-Buffer is a cache that contains information about changes of data blocks in the database buffer.

The Shared Pool is a cache used by all users. The main components of this pool are the dictionary cache and the library cache. The PGA (program global area) is used by a single oracle user process. It contains the user’s context area (cursors, variables etc.), as well as process information. The program global area is not sharable.

Each database instance has a set of processes distinguishable as user processes and oracle processes which are typically background processes.

DBWR is the process which manages the contents of the database buffer and the dictionary cache.

LGWR is the process which manages writing the contents of the redo-log-buffer to the redo-log files.

SMON is the process responsible for organizing space