Need help in analyzing size of a table

Question

Hi,
We have a table DUMMY_TABLE which has a clob column. We need to reduce the size of the table by updating the clob column. The table statistics before updating the clob column is showing 2MB of size as mentioned below. After we run the update script to update the clob column, the table statistics are as shown below (table size increased to 33MB). Can you please let us know, why is the table size getting increased after the update script.
Note: Before the update script the clob column has even bigger data.
Before running the update script:
Table Size - 2 MB
Blocks - 256
Extents - 17
After
running the update script:
Table Size - 33 MB
Blocks - 4224
Extents - 48
The query which we run to get the statistics is: “SELECT * FROM user_segments WHERE segment_name LIKE 'DUMMY_TABLE'”
Update script for updating clob column is:
DECLARE
data1 clob;
BEGIN
data1 :='Dear <%UserFirstName%>,
Below is the password you requested for the <%Company Name%>.
Password: <%xxx%>
To access the login page of the <%Company Name%>, please click on the following web-address:
<%ApplicationURL%><%UserIdentificationValue%>
If your email software does not support web links (i.e. clicking on the web-address does not take you directly to the <%Company Name%>), copy the above web-address into the "Address" or "Location" bar of your Internet web-browser in order to access the CareerTracker.
Sincerely,
Human Resource Department
<%Company Name%>
This is an automated email; please do not reply to this email address.';
UPDATE DUMMY_TABLE SET data = data1;
END;

Answer 1

Take the statistics of the tables and check again.
begin
DBMS_STATS.gather_table_stats(ownname=>'syslog',tabname=>'logs');
end;
Regards
Asif Kabir