Table Fragmentation

http://www.orafaq.com/node/1936


"dbms_redefinition"

SQL> create table TABLE1 (
2 no number,
3 name varchar2(20) default 'NONE',
4 ddate date default SYSDATE);

Table created.

SQL> alter table table1 add constraint pk_no primary key(no);

Table altered.

SQL> begin
2 for x in 1..100000 loop
3 insert into table1 ( no , name, ddate)
4 values ( x , default, default);
5 end loop;
6 end;
7 /

PL/SQL procedure successfully completed.

SQL> create or replace trigger tri_table1
2 after insert on table1
3 begin
4 null;
5 end;
6 /

Trigger created.

SQL> select count(*) from table1;

COUNT(*)
----------
100000

SQL> delete table1 where rownum <= 50000;

50000 rows deleted.

SQL> commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats('SCOTT','TABLE1');

PL/SQL procedure successfully completed.

SQL> select table_name, round((blocks*8),2)||'kb' "size"
2 from user_tables
3 where table_name = 'TABLE1';

TABLE_NAME size
------------------------------ ------------------------------------------
TABLE1 2960kb

SQL> select table_name, round((num_rows*avg_row_len/1024),2)||'kb' "size"
2 from user_tables
3 where table_name = 'TABLE1';

TABLE_NAME size
------------------------------ ------------------------------------------
TABLE1 822.69kb


SQL> --Minimum Privs required "DBA" role or "SELECT" on dbms_redefinition pkg
SQL> --First check table is condidate for redefinition.
SQL>
SQL> exec sys.dbms_redefinition.can_redef_table('SCOTT',-
> 'TABLE1',-
> sys.dbms_redefinition.cons_use_pk);

PL/SQL procedure successfully completed.

SQL> --After verifying that the table can be redefined online, you manually crea
te an empty interim table (in the same schema as the table to be redefined)
SQL>
SQL> create table TABLE2 as select * from table1 WHERE 1 = 2;

Table created.

SQL> exec sys.dbms_redefinition.start_redef_table ( 'SCOTT',-
> 'TABLE1',-
> 'TABLE2');

PL/SQL procedure successfully completed.

SQL> --This procedure keeps the interim table synchronized with the original tab
le.
SQL>
SQL> exec sys.dbms_redefinition.sync_interim_table ('SCOTT',-
> 'TABLE1',-
> 'TABLE2');

PL/SQL procedure successfully completed.

SQL> --Create PRIMARY KEY on interim table(TABLE2)
SQL> alter table TABLE2
2 add constraint pk_no1 primary key (no);

Table altered.

SQL> create trigger tri_table2
2 after insert on table2
3 begin
4 null;
5 end;
6 /

Trigger created.

SQL> --Disable foreign key on original table if exists before finish this proces
s.
SQL>
SQL> exec sys.dbms_redefinition.finish_redef_table ( 'SCOTT',-
> 'TABLE1',-
> 'TABLE2');

PL/SQL procedure successfully completed.

SQL> exec dbms_stats.gather_table_stats('SCOTT','TABLE1');

PL/SQL procedure successfully completed.

SQL> select table_name, round((blocks*8),2)||'kb' "size"
2 from user_tables
3 where table_name = 'TABLE1';

TABLE_NAME size
------------------------------ ------------------------------------------
TABLE1 1376kb

SQL> select table_name, round((num_rows*avg_row_len/1024),2)||'kb' "size"
2 from user_tables
3 where table_name = 'TABLE1';

TABLE_NAME size
------------------------------ ------------------------------------------
TABLE1 841.4kb

SQL> select status,constraint_name
2 from user_constraints
3 where table_name = 'TABLE1';

STATUS CONSTRAINT_NAME
-------- ------------------------------
ENABLED PK_NO1

SQL> select status ,trigger_name
2 from user_triggers
3 where table_name = 'TABLE1';

STATUS TRIGGER_NAME
-------- ------------------------------
ENABLED TRI_TABLE2

SQL> drop table TABLE2 PURGE;

Table dropped.