There are four structural types of database management systems: hierarchical, network, relational, and object-oriented.
Hierarchical Databases (DBMS), commonly used on mainframe computers, have been around for a long time. It is one of the oldest methods of organizing and storing data, and it is still used by some organizations for making travel reservations. Related fields or records are grouped together so that there are higher-level records and lower-level records, just like the parents in a family tree sit above the subordinated children. Based on this analogy, the parent record at the top of the pyramid is called the root record. A child record always has only one parent record to which it is linked, just like in a normal family tree.
In contrast, a parent record may have more than one child record linked to it. Hierarchical databases work by moving from the top down. A record search is conducted by starting at the top of the pyramid and working down through the tree from parent to child until the appropriate child record is found. Furthermore, each child can also be a parent with children underneath it. The advantage of hierarchical databases is that they can be accessed and updated rapidly because the tree-like structure and the relationships between records are defined in advance. Hierarchical databases are so rigid in their design that adding a new field or record requires that the entire database be redefined.
Types of DBMS: Network Databases
Network databases are similar to hierarchical databases by also having a hierarchical structure. There are a few key differences, however. Instead of looking like an upside-down tree, a network database looks more like a cobweb or interconnected network of records. In network databases, children are called membersand parents are called owners. The most important difference is that each child or member can have more than one parent (or owner). two limitations must be considered when using this kind of database. Similar to hierarchical databases, network databases must be defined in advance. There is also a limit to the number of connections that can be made between records.
Types of DBMS: Relational Databases
In relational databases, the relationship between data files is relational, not hierarchical Relational databases connect data in different files by using common data elements or a key field. Data in relational databases is stored in different tables, each having a key field that uniquely identifies each row. Relational databases are more flexible than either the hierarchical or network database structures.
Types of DBMS: Object-oriented Databases (OODBMS)
Able to handle many new data types, including graphics, photographs, audio, and video, object-oriented databases represent a significant advance over their other database cousins. an object-oriented database can be used to store data from a variety of media sources, such as photographs and text, and produce work, as output, in a multimedia format. Object-oriented databases have two disadvantages. First, they are more costly to develop. Second, most organizations are reluctant to abandon or convert from those databases that they have already invested money in developing and implementing.
CLUSTER COMPUTING: clustering means linking together two or more systems to handle variable workloads or to provide continued operation in the event one fails. Each computer may be a multiprocessor system itself. For example, a cluster of four computers, each with two CPUs, would provide a total of eight CPUs processing simultaneously. When clustered, these computers behave like a single computer and are used for load balancing, fault tolerance, and parallel processing.
Two or more servers that have been configured in a cluster use a heartbeat mechanism to continuously monitor each others health. Each server sends the other an I am OK message at regular intervals. If several messages or heartbeats are missed, it is assumed that a server has failed and the surviving server begins the failover operation. That is, the surviving server assumes the identity of the failed server in addition to its identity and recovers and restores the network interfaces, storage connections, and applications. Clients are then reconnected to their applications on the surviving server. The minimum requirements for a server cluster are
(a) two servers connected by a network, (b) a method for each server to access the others disk data, and (c) special cluster software like Microsoft Cluster Service (MSCS). The special software provides services such as failure detection, recovery, and the ability to manage the service as a single system.
Benefits of Clustering Technology
Availability, scalability and to a lesser extent, investment protection and simplified administration are all touted as benefits from clustering technology. Availability translates into decreased downtime, scalability translates into flexible growth, and investment protection and simplified administration translate into lowered cost of ownership. Clustered systems bring fault-tolerance and support for rolling upgrades. The most common uses of clustering technique are mission-critical database management, file/intranet data sharing, messaging, and general business applications.
PARALLEL COMPUTING: The Message Passing Interface (MPI) standard provides a common Application Programming Interface (API) for the development of parallel applications regardless of the type of multiprocessor system used. In the recent past, the Java programming language has made significant inroads as the programming language of choice for the development of a variety of applications in diverse domains.
What is Internet Protocol?
Internet Protocol is a set of technical rules that defines how computers communicate over a network.
There are currently two versions: IP version 4 (IPv4) and IP version 6 (IPv6).
What is IPv4?
IPv4 was the first version of Internet Protocol to be widely used, and accounts for most of todays Internet traffic. There are just over 4 billion IPv4 addresses. While that is a lot of IP addresses, it is not enough to last forever. What is IPv6?
IPv6 is a newer numbering system that provides a much larger address pool than IPv4. It was deployed in 1999 and should meet the worlds IP addressing needs well into the future.
File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host or to another host over a TCP-based network, such as the Internet.
The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web. Hypertext is a multi-linear set of objects, building a network by using logical links (the so-called hyperlinks) between the nodes (e.g. text or words). HTTP is the protocol to exchange or transfer hypertext. Secure Sockets Layer (SSL), are cryptographic protocols that provide communication security over the Internet. SSL encrypt the segments of network connections at the Application Layer for theTransport Layer, using asymmetric cryptography for key exchange, symmetric encryption for confidentiality, and message authentication codes for message integrity.
In computing, the Post Office Protocol (POP) is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IPconnection. POP and IMAP (Internet Message Access Protocol) are the two most prevalent Internet standard protocols for e-mail retrieval. Virtually all modern e-mail clients and servers support both. The POP protocol has been developed through several versions, with version 3 (POP3) being the current standard. Most webmail service providers such as Hotmail, Gmail and Yahoo! Mail also provide IMAP and POP3 service.
Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (e-mail) transmission across Internet Protocol (IP) networks. While electronic mail servers and other mail transfer agents use SMTP to send and receive mail messages, user-level client mail applications typically only use SMTP for sending messages to a mail server for relaying.
The User Datagram Protocol (UDP) is one of the core members of the Internet protocol suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without prior communications to set up special transmission channels or data paths. UDP is suitable for purposes where error checking and correction is either not necessary or performed in the application, avoiding the overhead of such processing at the network interface level.