Logical & Physical Structure

[nkumarin001]

Hi,

a) Why oracle architecture is divided into 2 types logical and physical structure?
b) What is the use of logical structure in oracle as it does not consume any space if so then what is the use of physical structure?

Regards,
Naveen

[debasisdas]

In Oracle the physical structures are:
---------------------------------------------------------
Datafiles
Control Files
Redo Log Files
Archive Log Files
Parameter Files
Alert and Trace Log Files
Backup Files

The Logical Structures are:
-----------------------------------------
Tablespaces
Oracle Data Blocks
Extents
Segments

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[avadhera]

Physical vs Logical can mean differnet things in different contexts . From Oracle perspective I think -

Physical : Because you can see the entites being physically present for example as OS Files(*.dbf etc)

Logical : The logical entites exist but you can not see them physically as such
blocks , extents , tablespaces all exist but not as the real physical structures .They are not real structures in physical sense, we combine certain structures and logically make them 1. Certain number of Bytes together logically making Blocks, Block together making extent , extent together logically making segments etc.

A tablespace can consist of one or more datafiles, you can see the datafiles(physical- as OS files) but not the tablespace(physically no ).Its existence is logical( one or more files make it). Similarly extents , you can not see them , it is a concept a logical view - they are just contiguous blocks , you do not seem them physically . So they do not exist in a way that you see real physical structures , their presence is just logical.

Hope I have not confused you more :-)

[debasisdas]

Yes avadhera you are absolutely right .

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Debasis