Shrink Oracle tables with LONG datatypes

Posted on 2008-06-09
Last Modified: 2013-12-19
What is the preferred method to shrink a table that contains a LONG Datatype?  I can not change the data type due to the third party software application.  I need to find a way to shrink these tables.

Would it benefit to have all tables with LONG's in them in a separate table space.  Tables range in size from 50 rows to 4mm rows.

Version is on Linux
Question by:mjimison1956
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LVL 35

Expert Comment

ID: 21744977
With a LONG, I beilieve the only option is exp/imp.
LVL 27

Expert Comment

ID: 21749349
LONG datatype is already depricated by oracle. A better way will be to re-create the tables using LOB data types. LOBs offer a lot of flexibilities and features.
See the illustration below.

SQL> create table t1(id number, val long);
Table created.
SQL> insert into t1 values(10, 'test');
1 row created.
SQL> commit;
Commit complete.
SQL> create table t2 as select id, to_lob(val) val from t1;
Table created.
SQL> desc t2
 Name                                            Null?    Type
 ----------------------------------------------- -------- --------
 ID                                                       NUMBER
 VAL                                                      CLOB
SQL> select * from t2;
        ID VAL
---------- -----------------------------------------------------
        10 test

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Author Comment

ID: 21749900
Will recreating the table require a change to the application?  I can not make any changes to the application code.

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LVL 35

Expert Comment

ID: 21759033
Changing from LONG to LOB will most likely require code changes in the applications.

Author Comment

ID: 21759090
Can not change the application due to cost and project.  What a mess.  Performance is terrible on these longs.

Any ideas on how to improve performance?

Accepted Solution

KICUSek earned 500 total points
ID: 21760667
My proposition:
1/ create separate tablespace with possibly large datablocks (16/32kB - depends on platform)
2/ migrate tables to new tablespace (exp/imp or other piece of code)

What operations are most common on this tables? inserts/updates/deletes or just selects?

Author Comment

ID: 21760710
The tables are used to set up a data scenario.  For example.  hundreds and thousands of insert, updates on the table, then a select is executed against the newly formatted data, passed to the application server, when the app server is complete a delete of all the newly inserted and updated data is executed.

Non sequential reads, I/O, CPU and performance is a nightmare.  I am constantly rebuilding indexes which also need shrinks.


Expert Comment

ID: 21760784
So i think step 1 could be beneficial.
Updates are performed on long columns or only on rest of them?

Author Comment

ID: 21760937
On all columns.  

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