I was little bit curious about DUMP function after writting Understanding Internal DATE Storage. So I did little bit reserach and find out following things about it.

The Oracle’s DUMP function returns a VARCHAR2 value consist of following three elements:

1. Internal DATATYE code
2. Length in bytes.
3. Internal representation of the expression.

Its Syntax is as follows:

dump( expression, [return_format], [start_position], [length] )

expression is the expression or value to analyze and is the mandatory parameter.

return_format determines the format of the return value and is an optional parameter.

Valid values for the return_format is 8,10,16,17,1008,1010,1016 and 1017.

These values have following meaning:
8 - octal notation
10 - decimal notation
16 - hexadecimal notation
17 - single characters
1008 - octal notation with the character set name
1010 - decimal notation with the character set name
1016 - hexadecimal notation with the character set name
1017 - single characters with the character set name

start_position and length determines which portion of the internal representation to display and is an optional parameter.

If these optional parameters are omitted, the dump function will display the entire internal representation in decimal notation.