Oracle Database can connect and interact with any database globally using inbuilt networking features.
In this chapter, we will discuss about Networking, Listener, and Shared Server.
DBA should understand some essential features comprising the network such as:
Complexity issues: How many and what type of clients connect to the Database, the location of clients, types of clients supported, expected growth of the network, protocols involved in communication etc.
Security issues: How connections are to be secure, possibility of tampering of information, need of centralised authentication, hardware and software requirements, modifications need to meet the security requirements, procedural changes, staffing pattern etc.
Adaptability issues: Interfacing between existing and new systems.
The issues / actions required in implementing the above tasks comprise DBA's responsibilities with respect to Network Administration.
There are 3 basic types of network configurations in designing Oracle Database Network.
Single tier Two tier n-tier
Single Tier Architecture: The terminals are connected directly to the server in serial connection.
Referred to as green-screen applications derived from IBM 3270 terminals which had green screens, Single Tier architecture is associated with Mainframe-type applications.. Simplest to configure and administer. Terminals are directly connected to the host computer. No protocols and multiple operating systems.
When this type of configuration was used, terminals were nongraphical and were chareacter-based devices.
Scalability and flexibility features were lacking as the entire processing must take place on the server, which is a performance issue.
Two-Tier Architecture: Referred to as client/server computing, terminals are connected to the server over a network using network protocol. TCP/IP is a popular protocol and has become de facto standard of network computing. In this architecture, the client and the server must understand the protocol used.
Client computing introduces GUI and is simpler and more flexible than character based connections.
The slash between Client/Server is an invisible component of the 2-tier architecture. This architecture too, lacks advantage of scalability.
n-Tier Architecture: An extension of 2-tier architecture, n-tier architecture introduces middleware components such as application servers or web servers situated between client and the server. It divides application processing work between client and the server on 3 or more machines.
Oracle Net features:
Connectivity Manageability Scalability Security Accessibility
Connectivity: Provides ability to connect databases over network using multiple protocols, using multiple operating systems and Java / JDBC Support.
Manageability: Facilitates connection to databases using web browser interface, maintaining transparency of various database components' locations, use of Directory Naming protocol etc.
Scalability: Allowing multi-dimentional growth of database without compromising performance. Scalability features include Shared Server and Connection Manager.
Oracle Shared Server: An optional configuration of Oracle Server allowing large number of concurrent connections with the same resources. Meaning, resources are shared by groups of users. Connection Manager: A middleware solution that provides 3 additional scalability features.
Multiplexing Network Access, Cross-protocol connectivity.
Security: Oracle Net provides security and advanced security features as the database is accessed over network and checks data tampering.
Accessibility: Ability to connect to non-database data sources without needing to convert the non-database data.