Oracle Database Discussions

Source OS : Sun Microsystems Inc. SunOS 5.5.1

My actual size of the database are as follows:

SQL> select sum(bytes) from dba_data_files;

SUM(BYTES)
----------
3227516928

But size of my dmp file is as follows:

dhs3 41: ls -ltr dawar.dmp
-rw-r--r-- 1 oracle7 dba 51577856 Sep 2 12:07 dawar.dmp

Here what I got in Linux server (Destination) after FTP

oracle@dhshrwits:~/Documents> ls -ltr dawar.dmp
-rw-r--r-- 1 oracle oinstall 51563371 2004-09-02 12:38 dawar.dmp

All sizes have some differences.

Case Study:
My goal is to export entire database, oracle 7.3.4 from sunOS 5.5.1. and put in the Linux server through ftp.
The file name is dawar.dmp which contains all data.

I tested exp and ftp.

Please confirm my all steps.
I did telnet to my Sun Box from Linux Sever.
Logon to sqlplus on Sun OS via telnet where Oracle 7.3.4 existed.

Connected to: Oracle7 Server Release 7.3.4.5.0 - Production
With the parallel query option
PL/SQL Release 2.3.4.5.0 - Production
Enter array fetch buffer size: 4096 >

Export file: expdat.dmp > dawar.dmp

(1)E(ntire database), (2)U(sers), or (3)T(ables): (2)U > 1

Export grants (yes/no): yes > yes

Export table data (yes/no): yes > yes

Compress extents (yes/no): yes >

Export done in US7ASCII character set

About to export the entire database ...
. exporting tablespace definitions
....................
.................

Export terminated successfully without warnings.

dhs3 41: ls -ltr dawar.dmp
-rw-r--r-- 1 oracle7 dba 51577856 Sep 2 12:07 dawar.dmp

exit from sqlplus and telnet sun OS.

Now from Linux server I run ftp from the directory I like to transfer dawar.dmp as:
oracle@dhshrwits:~/Documents> ftp ipaddress of Sun OS
Logon as a Oracle user.

ftp> get dawar.dmp
local: dawar.dmp remote: dawar.dmp
227 Entering Passive Mode (159,225,155,29,146,23)
150 ASCII data connection for dawar.dmp (159.225.140.75,36190) (51577856 bytes).
226 ASCII Transfer complete.
51879696 bytes received in 19:54 (42.41 KB/s)
ftp> exit

File has transfer to the Linux Server.

LINUX SERVER (DESTINATION)
oracle@dhshrwits:~/Documents> ls -ltr dawar.dmp
-rw-r--r-- 1 oracle oinstall 51563371 2004-09-02 12:38 dawar.dmp
oracle@dhshrwits:~/Documents>

Am I missing any thing in the whole process?
If not, so why the size has of a db has big difference than dawar.dmp?

Any feedback will be appreciated.

Regards,
D