The following query can be used to list the database objects of the user:
select object_name, object_type from user_objects;
There are couple of entries where the object_type is LOB.
How can these LOB objects be dropped in Oracle?
One scenario where you can see a LOB in user_objects
but the join to user_lobs
doesn't find anything is if the table has already been dropped, but is in the recycle bin.
create table t42 (my_clob clob);
table T42 created.
As expected, Justin's query shows you the column:
select l.table_name,
l.column_name,
l.segment_name lob_name
from user_lobs l
join user_objects o
on( o.object_name = l.segment_name );
TABLE_NAME COLUMN_NAME LOB_NAME
----------- ----------- ------------------------------
T42 MY_CLOB SYS_LOB0000133310C00001$$
drop table t42;
table T42 dropped.
Now Justin's query doesn't find anything:
select l.table_name,
l.column_name,
l.segment_name lob_name
from user_lobs l
join user_objects o
on( o.object_name = l.segment_name );
no rows selected
But it's still in user_objects
:
select object_name, object_type, status from user_objects
where object_type like 'LOB%';
OBJECT_NAME OBJECT_TYPE STATUS
------------------------------ ------------------- -------
SYS_LOB0000133328C00001$$ LOB VALID
And you can see it in the recycle bin:
select * from user_recyclebin;
OBJECT_NAME ORIGINAL_NAME OPERATION TYPE TS_NAME CREATETIME DROPTIME DROPSCN PARTITION_NAME CAN_UNDROP CAN_PURGE RELATED BASE_OBJECT PURGE_OBJECT SPACE
------------------------------ -------------------------------- --------- ------------------------- ------------------------------ ------------------- ------------------- ---------- -------------------------------- ---------- --------- ---------- ----------- ------------ ----------
SYS_IL0000133310C00001$$ SYS_IL0000133310C00001$$ DROP LOB INDEX USERS 2013-08-22:08:33:21 2013-08-22:08:33:21 1.0E+13 NO NO 133310 133310 133310 0
SYS_LOB0000133310C00001$$ SYS_LOB0000133310C00001$$ DROP LOB USERS 2013-08-22:08:33:21 2013-08-22:08:33:21 1.0E+13 NO NO 133310 133310 133310 0
BIN$5IUNXtWkUXLgQwEAAH9TlQ==$0 T42 DROP TABLE USERS 2013-08-22:08:33:21 2013-08-22:08:33:21 1.0E+13 YES YES 133310 133310 133310 0
The LOB still exists on disk and is using storage, which I guess is what you're concerned about. So to sort of answer your question, to really drop the LOB and release its storage you need to purge the whole table:
purge table t42;
table purged.
select object_name, object_type, status from user_objects
where object_type like 'LOB%';
no rows selected
Interestingly you don't see this effect if you name the LOB segment:
create table t42 (my_clob clob)
lob (my_clob) store as my_clob_segment;
Repeating the steps above, the entry has gone from user_objects
after the drop
.
drop table t42;
table T42 dropped.
select object_name, object_type, status from user_objects
where object_type like 'LOB%';
no rows selected
select * from user_recyclebin;
OBJECT_NAME ORIGINAL_NAME OPERATION TYPE TS_NAME CREATETIME DROPTIME DROPSCN PARTITION_NAME CAN_UNDROP CAN_PURGE RELATED BASE_OBJECT PURGE_OBJECT SPACE
------------------------------ -------------------------------- --------- ------------------------- ------------------------------ ------------------- ------------------- ---------- -------------------------------- ---------- --------- ---------- ----------- ------------ ----------
BIN$5IUNXtWnUXLgQwEAAH9TlQ==$0 MY_CLOB_SEGMENT DROP LOB USERS 2013-08-22:08:36:41 2013-08-22:08:36:41 1.0E+13 NO NO 133316 133316 133316 0
BIN$5IUNXtWoUXLgQwEAAH9TlQ==$0 T42 DROP TABLE USERS 2013-08-22:08:36:41 2013-08-22:08:36:41 1.0E+13 YES YES 133316 133316 133316 0
SYS_IL0000133316C00001$$ SYS_IL0000133316C00001$$ DROP LOB INDEX USERS 2013-08-22:08:36:41 2013-08-22:08:36:41 1.0E+13 NO NO 133316 133316 133316 0
The storage is still being used of course and you still need to purge to free it, it just looks a bit more consistent in the data dictionary. So this looks like a (very minor) bug, maybe, at most. It might be related to the behaviour referred to in support note 394442.1.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With