Oracle: how to find out storage space used by a table?
Via OEM 10g,
- Connect to the database as usual
- Click on the
Schematab - On the
Tableslink within Database Objects - Enter the schema name and object name (optional) and click
Go - Use the radio button to select the table you want to look at and click on
Edit(Don't click on the table name link) - Click on the
Segmentstab (and wait...) - You will see the size of the table data and the indexes used.
OK, that technically answered your question. But a better way is:
- Logon using SQLPLUS
- Run the script from Vincent.
I like to save the script as t.sql as a quick reference
COLUMN size_mb FORMAT '999,999,990.0'
COLUMN num_rows FORMAT '999,999,990'
COLUMN fmt_short FORMAT A24
COLUMN owner FORMAT A16
COLUMN table_name LIKE fmt_short
COLUMN tablespace_name LIKE fmt_short
SET LINESIZE 200
SET AUTOTRACE OFF
COMPUTE SUM OF size_mb ON REPORT
BREAK ON REPORT
SELECT
lower( owner ) AS owner
,lower(table_name) AS table_name
,tablespace_name
,num_rows
,blocks*8/1024 AS size_mb
,pct_free
,compression
,logging
FROM all_tables
WHERE owner LIKE UPPER('&1')
OR owner = USER
ORDER BY 1,2;
CLEAR COMPUTES
CLEAR BREAKS
The space used by a table is the space used by all its extents:
SELECT SUM(bytes), SUM(bytes)/1024/1024 MB
FROM dba_extents
WHERE owner = :owner
AND segment_name = :table_name;
SUM(BYTES) MB
---------- ----------
3066429440 2924,375
Are you sure that the original approach using the all_tables view includes LOB extents? I would think not. Here is one that I am finding useful:
with da as (
SELECT owner, segment_name, SUM(bytes)/1024/1024 size_mb
FROM dba_extents
group by rollup(owner, segment_name)
) select owner, segment_name, size_mb, round(size_mb/total_mb*100)
from da
cross join (
select size_mb as total_mb
from da t where owner is null and segment_name is null
)
order by size_mb desc
It shows me what's using the most space.
After some google searches and experiments, I've built the following query, which provides to my mind the most accurate result. For an oracle user, it provides the free/used/total space by Table and segment type (TABLE *, INDEX *, LOB *). You can easily extend it in order to provide additional statistics like block counts.
Typical Output is:
table ; segment type ; used (mb) ; unused (mb) ; total (mb)
user ; INDEX ; 0,78; 0,00; 0,78
user ; LOBINDEX ; 0,15; 0,00; 0,15
user ; LOBSEGMENT ; 3,48; 1,19; 4,67
user ; TABLE ; 12,11; 2,74; 14,85
address ; INDEX ; 0,12; 0,00; 0,12
(...)
Script:
DECLARE
input_owner NVARCHAR2(128) := 'MY_ORACLE_OWNER';
segment_size_blocks NUMBER;
segment_size_bytes NUMBER;
used_blocks NUMBER;
used_bytes NUMBER;
expired_blocks NUMBER;
expired_bytes NUMBER;
unexpired_blocks NUMBER;
unexpired_bytes NUMBER;
total_blocks NUMBER;
total_bytes NUMBER;
unused_blocks NUMBER;
unused_bytes NUMBER;
last_ext_file_id NUMBER;
last_ext_blk_id NUMBER;
last_used_blk NUMBER;
result_table NVARCHAR2(128);
result_segment_type NVARCHAR2(128);
result_used_mb NUMBER;
result_unused_mb NUMBER;
result_total_mb NUMBER;
CURSOR cur
IS
SELECT
s.segment_name AS segment_name,
s.owner AS segment_owner,
s.partition_name AS partition_name,
s.segment_type AS segment_type,
CASE WHEN s.segment_type IN ('TABLE', 'TABLE PARTITION', 'TABLE SUBPARTITION')
THEN s.segment_name
WHEN s.segment_type IN ('INDEX', 'INDEX PARTITION', 'INDEX SUBPARTITION')
THEN (SELECT i.table_name
FROM dba_indexes i
WHERE s.segment_name = i.index_name AND s.owner = i.owner)
WHEN s.segment_type IN ('LOBSEGMENT', 'LOB PARTITION')
THEN (SELECT l.table_name
FROM dba_lobs l
WHERE s.segment_name = l.segment_name AND s.owner = l.owner)
WHEN s.segment_type IN ('LOBINDEX')
THEN (SELECT l.table_name
FROM dba_lobs l
WHERE s.segment_name = l.index_name AND s.owner = l.owner)
ELSE 'Unknown'
END AS table_name,
s.bytes AS segment_bytes
FROM dba_segments s
WHERE owner = input_owner
ORDER BY table_name, segment_type;
BEGIN
dbms_output.put_line('table ; segment type ; used (mb) ; unused (mb) ; total (mb)');
FOR ro IN cur
LOOP
result_table := ro.table_name;
result_segment_type := ro.segment_type;
IF ro.segment_type IN ('TABLE', 'INDEX')
THEN
dbms_space.unused_space(
segment_owner => ro.segment_owner,
segment_name => ro.segment_name,
segment_type => ro.segment_type,
total_blocks => total_blocks,
total_bytes => total_bytes,
unused_blocks => unused_blocks,
unused_bytes => unused_bytes,
last_used_extent_file_id => last_ext_file_id,
last_used_extent_block_id => last_ext_blk_id,
last_used_block => last_used_blk);
result_used_mb := (total_bytes - unused_bytes) / 1024 / 1024;
result_unused_mb := unused_bytes / 1024 / 1024;
result_total_mb := total_bytes / 1024 / 1024;
ELSIF ro.segment_type IN ('LOBSEGMENT')
THEN
dbms_space.space_usage(
segment_owner => ro.segment_owner,
segment_name => ro.segment_name,
segment_type => 'LOB',
partition_name => ro.partition_name,
segment_size_blocks => segment_size_blocks,
segment_size_bytes => segment_size_bytes,
used_blocks => used_blocks,
used_bytes => used_bytes,
expired_blocks => expired_blocks,
expired_bytes => expired_bytes,
unexpired_blocks => unexpired_blocks,
unexpired_bytes => unexpired_bytes
);
result_used_mb := used_bytes / 1024 / 1024;
result_unused_mb := (segment_size_bytes - used_bytes) / 1024 / 1024;
result_total_mb := segment_size_bytes / 1024 / 1024;
ELSE
-- TODO ??
result_used_mb := ro.segment_bytes / 1024 / 1024;
result_unused_mb := 0;
result_total_mb := result_used_mb + result_unused_mb;
END IF;
dbms_output.put_line(
RPAD(result_table, 30) || '; ' ||
RPAD(result_segment_type, 20)|| '; ' ||
TO_CHAR(result_used_mb / 1024 / 1024, '999999999990D00')|| '; ' ||
TO_CHAR(result_unused_mb / 1024 / 1024, '999999999990D00')|| '; ' ||
TO_CHAR(result_total_mb / 1024 / 1024, '999999999990D00'));
END LOOP;
END;