What is Mapping In Database Environment

Mapping

Mapping is the process of converting one level to another level. In this process, the data
at one level is related to the data at another level. There are two levels of mapping:

1. From the conceptual level to the internal level
2. From the external level to the conceptual level

Conceptual / Internal Mapping

The conceptual/internal mapping defines the correspondence between the conceptual view and the stored database. It specifies how conceptual records and fields are represented at the internal level. If the structure of the stored database is changed, then the conceptual/internal mapping must be changed accordingly so that the conceptual schema can remain consistent. It is the responsibility of DBA to manage such change.

 

External/Conceptual Mapping
An external/conceptual mapping defines the correspondence between a particular external view and a conceptual view. Generally, the differences between these two levels are similar to the differences between conceptual view and stored database. For example, fields can have different data types, fields and record names can be changed, several conceptual fields can be combined into a single field. Any number of external views can exist at the same time. Any number of users can share a given external view and different external views can overlap each other.

The representation of data at different levels of database architecture. The data is stored in binary format at the physical level. It is separate from the internal view of data. The data is prefixed with Block Header (BH) and Record Header (RH). The record header is used with every record. The block header is used with a group of records.

• Database Environment