delayed block cleanout的例子：
SQL> select * from tt
ID NAME
---------- --------------------
1 xxxxxxx
2 xxxxxxx
3 xxxxxxx
SQL> update tt set name='111111111' where id=1;
1 row updated.
SQL> update tt set name='222222222222' where id=2;
1 row updated.
SQL> update tt set name='3333333333' where id=3;
1 row updated.
SQL> alter session set events 'immediate trace name flush_cache';
Session altered.
SQL> commit;
Commit complete.
SQL> alter system dump datafile 4 block 92;
System altered.
查看dump出来的内容之后，发现block中海油ITL的信息。如下为block dump的信息:
---===========================================
Itl Xid Uba Flag Lck Scn/Fsc
0x01 0x0005.003.00000383 0x00801a95.012b.15 --U- 3 fsc 0x0000.00194a1e
0x02 0x0008.015.00000385 0x00800204.0123.03 C--- 0 scn 0x0000.001949e9
data_block_dump,data header at 0x8ee5264
===============
tsiz: 0x1f98
hsiz: 0x18
pbl: 0x08ee5264
bdba: 0x0100005c
76543210
flag=--------
ntab=1
nrow=3
frre=-1
fsbo=0x18
fseo=0x1f16
avsp=0x1f4c
tosp=0x1f4c
0xe:pti[0] nrow=3 offs=0
0x12:pri[0] offs=0x1f3a
0x14:pri[1] offs=0x1f27
0x16:pri[2] offs=0x1f16
block_row_dump:
tab 0, row 0, @0x1f3a
tl: 16 fb: --H-FL-- lb: 0x1 cc: 2
col 0: [ 2] c1 02
col 1: [ 9] 31 31 31 31 31 31 31 31 31
tab 0, row 1, @0x1f27
tl: 19 fb: --H-FL-- lb: 0x1 cc: 2
col 0: [ 2] c1 03
col 1: [12] 32 32 32 32 32 32 32 32 32 32 32 32
tab 0, row 2, @0x1f16
tl: 17 fb: --H-FL-- lb: 0x1 cc: 2
col 0: [ 2] c1 04
col 1: [10] 33 33 33 33 33 33 33 33 33 33
end_of_block_dump
End dump data blocks tsn: 4 file#: 4 minblk 92 maxblk 92
---=====================================================
下次访问更新的时候，就可以清除。