System Tablespace Usage

Question

Hi to all,
I am a bit new to DBA admin and have was wondering how I can see what size each table is in the System Tablespace and list them in order of size?
Thanks to all that reply

Answer 1

sybrand_b wrote:
select t.owner, t.table_name, s.bytes/1024 kb
from dba_segments s inner join dba_tables t
on (s.segment_name = t.table_name)
order by 3 desc;
Wrong.
Joiining dba_tables to dba_segments eliminates information about lots of things that the user may want to see, for example:
<ul>
Index organized tables - their data segments have an index component and an overflow component, and only the overflow appears from this query.
Nested tables (holding data from tables with columns of type table) disappear from this view
Tables in clusters - the segment_name is the cluster name (and the clusters in the system tablespace can be big).
LOB segments - shouldn't space due to the LOB columns in the tables be reported as well ? They don't show up in dba_tables, so will disappear from this report.
</ul>
To the OP.
If you want detailed information about space usage in the SYSTEM tablespace it's not a trivial task. A starting point is simply to list the segments allocated in the tablespace. If you want to drill down from their, you need to know what the segment type represents and where it comes from. For more detail you may then want to consider how much of the space inside the segment has been used and how much may have been overallocated.
Start with something simple like:
column segment_name format a32
select
     owner, segment_name, segment_type, bytes/1024 kb
from
     dba_segments
where
     tablespace_name = 'SYSTEM'
order by
     kb desc,
     owner
;Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
To post code, statspack/AWR report, execution plans or trace files, start and end the section with the tag {noformat}{noformat} (lowercase, curly brackets, no spaces) so that the text appears in fixed format.
"There's no sense in being precise when you don't even know what you're talking about"
John von Neumann