Stack is a collection of objects that works in LIFO (Last in First out) mechanism while Queue is FIFO (First in First out). This means that the object that is inserted first is removed last in a stack while an object that is inserted first is removed first in a queue.

Stack unwinding is a process of calling all destructors for all automatic objects constructed at run time when an exception is thrown. Destructors are called between the places where the exception was thrown and where it is caught.

A Stack is a linear structure in which insertions and deletions are always made at one end i.e the top - this is termed as last in, first out (LIFO). Stacks are useful when we need to check some syntex errors like missing parentheses. 

- Friend classes are useful when a class wants to hide features from users which are needed only by another, tightly coupled class. 

- Implementation details can be kept safe by providing friend status to a tightly cohesive class.

According to one-definition rule, C++ constructs must be identically defined in every compilation unit they are used in. 

As per ODR, two definitions contained in different source files are called to be identically defined if they token-for-token identical. The tokens should have same meaning in both source files. 

Identically defined doesn’t mean character-by-character equivalence. Two definitions can have different whitespace or comments and yet be identical.

i.) Const - This variable means that if the memory is initialised once, it should not be altered by a program. 

ii.) Volatile - This variable means that the value in the memory location can be altered even though nothing in the program code modifies the contents. 

iii.) Mutable - This variable means that a particular member of a structure or class can be altered even if a particular structure variable, class, or class member function is constant.

Insert image into a table

Create the following table:

      create table pics_table (

      bfile_id number,

      bfile_desc varchar2(30),

      bfile_loc bfile,

      bfile_type varchar2(4))

      TABLESPACE appl_data

      storage (initial 1m next 1m pctincrease 0) 

Insert Query:

      INSERT INTO pics_table

      VALUES(4,'test image',bfilename('GIF_FILES','Test.JPG'),'JPEG'); 

- Clustering means one than one database server configured for the same user connection. When users connect, one of the server’s responds and connects based on availability. The user is completely ignorant of the fact that there are more than one database servers. It demands high cost due to infrastructure needs. Clustering is hence done on server level.

- Mirroring means, one has many configured databases on the same server. Mirrors are basically copies of the original database. Mirroring is hence done on database level.