Network Database or Network Model in DBMS
The network database or network model uses the plex structure as its basic data structure. A network is a directed graph consisting of nodes connected by links or directed arcs. The nodes corresponds to record types and the links to pointers or relationships. All the relationship are hardwired or pre-computed and build into structure of database itself because they are very efficient in space utilization and query execution time.
The network data structure looks like a tree structure except that a dependent node which is called a child or member, may have more than one parent or owner node.All figure shows the network model –
The network data structure looks like a tree structure except that a dependent node which is called a child or member, may have more than one parent or owner node.All figure shows the network model –
 |
| Figure 1 |
A diagram called as Bachman Diagram is used to represent a network data structure. The nodes in the network are replaced by rectangles that represent records and links are shown by lines connecting the rectangles.
A plex structure with two record types is shown / Example of Network Database :
 |
| Figure 2 |
Another Example of Network Database is :
Operations on Network Model/Network Database
- Insertion- In the above figure, it is clear that a new part or supplier can easily be inserted.
- Deletion- For deletion only link is to be removed and no information will be lost. For example, to remove PART 2, we delete the connector line between suppliers.
- Updation- Updation is also easy, for example, suppose SUPPLIER B supplies PART 1 in place of SUPPLIER 2, so, updation will be successfully done by changing the link of SUPPLIER B from PART 2 to PART 1.
ADVANTAGES OF NETWORK MODEL-
The major advantage of network model are-
1.) Conceptual simplicity-Just like the hierarchical model,the network model is also conceptually simple and easy to design.
2.) Capability to handle more relationship types-The network model can handle the one to many and many to many relationships which is real help in modeling the real life situations.
3.) Ease of data access-The data access is easier and flexible than the hierarchical model.
4.) Data integrity- The network model does not allow a member to exist without an owner.
5.) Data independence- The network model is better than the hierarchical model in isolating the programs from the complex physical storage details.
6.) Database standards
DIS-ADVANTAGE OF NETWORK MODEL-
1.) System complexity- All the records are maintained using pointers and hence the whole database structure becomes very complex.
2.) Operational Anomalies- The insertion,deletion and updating operations of any record require large number of pointers adjustments.
3.) Absence of structural independence-structural changes to the database is very difficult.