Mumbai University > Information Technology > Sem 5 > Advanced Database Management System

Marks: 10M

Year: May 2016

Object Identity:

Any object has 2 properties i.e. state & behaviour hence, it’s similar to the program variable but object has complex structure.

• There are two types of object :-
  • Transient object
  • Persistent object

1.) Transient object: - These objects exist during the execution but destroy ones the program terminates.

2.) Persistent object: - These objects persist & store into database even if program terminate. Whenever any object created DBMS assigns unique identifier called as object identity & its abbreviated as OID. OID is used for two purposes.

• To identity each objects uniquely.
• Make reference to another object.
• Properties of OID
• Its unique
• Its system generated
• Its invisible to the user
• It’s not possible t perform operation on OID
• It’s in mutable i.e. once its generated
• It cannot be regenerated
• It has along integer values
• Object structure

Every object has internal structure that can be specified by using 6 types of type constructor (AST LAM)…