what is Data Independence.&types.

 Data Independence:-

                                The architecture of the DBMS can be viewed as a 3-level system comprising the                                            following:  

 The internal or the physical level where the data resides. The conceptual level which is the level of the DBMS functions. The external level is the level of the application programs or the end user. Changes in the lower level without affecting the upper level is data independence. 

In simple words, the ability to modify a schema definition in one level without affecting a schema definition in the next higher level is called data independence.

There are two levels of data independence:

 i) Physical data independence

 ii) Logical data independence

i) Physical data independence: It is the ability to modify the schema definition at the physical level without affecting the schema at the conceptual level.

ii) Logical data independence: It is the ability to modify the conceptual schema without causing any changes in the schema at view level. It ensures that the application programs remain the same, modifications at the conceptual level are necessary whenever logical structures of the database get altered because of some unavoidable reasons. External Leve