A DBA's job is to assure the efficiency, security, and integrity of databases under his care. These objectives correspond to tasks 1, 2 and 3 respectively.
Entering data into databse is a daily operation belonging to the database manager / users, so it is not a DBA's task.
The Application layer creates a message.
The Application layer passes the message to the Presentation layer.
The Presentation layer encapsulates the message by adding information to it. Information is usually added only at the beginning of the message (called a header); however, some layers also add material at the end of the message (called a footer)
The process of passing the message down and adding layer-specific information continues until the message reaches the Physical layer.
At the Physical layer, the message is converted into electrical impulses that represent bits and is transmitted over the physical connection.
The receiving computer captures the bits from the physical connection and re-creates the message in the Physical layer.
The Physical layer converts the message from bits into a Data Link frame and sends the message up to the Data Link layer.
The Data Link layer strips its information and sends the message up to the Network layer.
This process of deencapsulation is performed until the message reaches the Application layer.
When the message reaches the Application layer, the data in the message is sent to the intended software recipient.
