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这篇CFSDN的博客文章关于ORACLE通过file_id与block_id定位数据库对象遇到的问题引发的思考由作者收集整理,如果你对这篇文章有兴趣,记得点赞哟.
在ORACLE中,我们可以通过file_id(file#)与block_id(block#)去定位一个数据库对象(object)。例如,我们在10046生成的trace文件中file#=4 block#=266 blocks=8,那么我可以通过下面两个SQL去定位对象 。
SQL 1:此SQL效率较差,执行时间较长.
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SELECT
OWNER,
SEGMENT_NAME,
SEGMENT_TYPE,
TABLESPACE_NAME
FROM
DBA_EXTENTS
WHERE
FILE_ID =&FILE_ID
AND
&BLOCK_ID
BETWEEN
BLOCK_ID
AND
BLOCK_ID + BLOCKS - 1;
|
SQL 2:此SQL效率较快(ORACLE 10g 中没有CACHEHINT字段) 。
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SELECT OBJD,
FILE
#,
BLOCK
#,
CLASS
#,
TS
#,
CACHEHINT,
STATUS,
DIRTY
FROM V$BH
WHERE FILE
# = &FILE_ID
AND BLOCK
# = &BLOCK_ID;
SELECT OWNER, OBJECT_NAME FROM DBA_OBJECTS WHERE OBJECT_ID=&OBJECT_ID;
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下面通过一个例子来演示一下,详情如下所示 。
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SQL> COL OWNER
FOR
A12;
SQL> COL SEGMENT_NAME
FOR
A32;
SQL>
SELECT
OWNER ,
2 SEGMENT_NAME ,
3 HEADER_FILE ,
4 HEADER_BLOCK
5
FROM
DBA_SEGMENTS
6
WHERE
OWNER=
'TEST'
AND
SEGMENT_NAME=
'EMPLOYEE'
;
OWNER SEGMENT_NAME HEADER_FILE HEADER_BLOCK
------------ -------------------------------- ----------- ------------
TEST EMPLOYEE 4 266
SQL>
SQL>
SELECT
OWNER,
2 SEGMENT_NAME,
3 SEGMENT_TYPE,
4 TABLESPACE_NAME
5
FROM
DBA_EXTENTS
6
WHERE
FILE_ID = 4
7
AND
266
BETWEEN
BLOCK_ID
AND
BLOCK_ID + BLOCKS - 1;
OWNER SEGMENT_NAME SEGMENT_TYPE TABLESPACE_NAME
------------ -------------------------------- ------------------ -----------------
TEST EMPLOYEE
TABLE
USERS
SQL>
SQL>
SELECT
OBJD,
2 FILE#,
3 BLOCK#,
4 CLASS#,
5 TS#,
6 CACHEHINT,
7 STATUS,
8 DIRTY
9
FROM
V$BH
10
WHERE
FILE# = 4
11
AND
BLOCK# = 266;
OBJD FILE# BLOCK# CLASS# TS# CACHEHINT STATUS D
---------- ---------- ---------- ---------- ---------- ---------- ---------- -
76090 4 266 4 4 15 cr N
76090 4 266 4 4 15 cr N
76090 4 266 4 4 15 cr N
SQL>
SELECT
OWNER, OBJECT_NAME
FROM
DBA_OBJECTS
WHERE
OBJECT_ID=76090;
OWNER OBJECT_NAME
------------ ------------------------------------------------------------
TEST EMPLOYEE
clip_image001
|
昨天在群里讨论一个关于空闲块的问题时,我验证测试时,发现一个奇怪的现象,使用下面SQL找到了一个最大空闲块.
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SELECT
UPPER
(F.TABLESPACE_NAME)
AS
"表空间名"
,
D.TOT_GROOTTE_MB
AS
"表空间大小(M)"
,
D.TOT_GROOTTE_MB - F.TOTAL_BYTES
AS
"已使用空间(M)"
,
TO_CHAR(ROUND((D.TOT_GROOTTE_MB - F.TOTAL_BYTES) / D.TOT_GROOTTE_MB * 100,2),
'990.99'
)
AS
"使用比"
,
F.TOTAL_BYTES
AS
"空闲空间(M)"
,
F.MAX_BYTES
AS
"最大空闲块(M)"
FROM
(
SELECT
TABLESPACE_NAME,
ROUND(
SUM
(BYTES) / (1024 * 1024), 2) TOTAL_BYTES,
ROUND(
MAX
(BYTES) / (1024 * 1024), 2) MAX_BYTES
FROM
SYS.DBA_FREE_SPACE
GROUP
BY
TABLESPACE_NAME
) F,
(
SELECT
DD.TABLESPACE_NAME,
ROUND(
SUM
(DD.BYTES) / (1024 * 1024), 2) TOT_GROOTTE_MB
FROM
SYS.DBA_DATA_FILES DD
GROUP
BY
DD.TABLESPACE_NAME
) D
WHERE
D.TABLESPACE_NAME = F.TABLESPACE_NAME;
SELECT
FILE_ID,BLOCK_ID, BYTES,BLOCKS
FROM
DBA_FREE_SPACE
WHERE
TABLESPACE_NAME=&TABLESPACE_NAME
ORDER
BY
BYTES
DESC
;
|
然后我发现使用上面两个SQL查不到对应的对象。如下截图所示:
后面查了一下资料,发现在Oracle Database 10g引入了回收站功能后,会将回收站(RECYCLEBIN$)中的空间计算为自由空间,加入到dba_free_space字典中。在$ORACLE_HOME/rdbms/admin/catspace.sql中,你可以找到视图DBA_FREE_SPACE的定义,脚本如下:
ORACLE 10g中DBA_FREE_SPACE的定义:
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create
or
replace
view
DBA_FREE_SPACE
(TABLESPACE_NAME, FILE_ID, BLOCK_ID,
BYTES, BLOCKS, RELATIVE_FNO)
as
select
ts.
name
, fi.file#, f.block#,
f.length * ts.blocksize, f.length, f.file#
from
sys.ts$ ts, sys.fet$ f, sys.file$ fi
where
ts.ts# = f.ts#
and
f.ts# = fi.ts#
and
f.file# = fi.relfile#
and
ts.bitmapped = 0
union
all
select
/*+ ordered use_nl(f) use_nl(fi) */
ts.
name
, fi.file#, f.ktfbfebno,
f.ktfbfeblks * ts.blocksize, f.ktfbfeblks, f.ktfbfefno
from
sys.ts$ ts, sys.x$ktfbfe f, sys.file$ fi
where
ts.ts# = f.ktfbfetsn
and
f.ktfbfetsn = fi.ts#
and
f.ktfbfefno = fi.relfile#
and
ts.bitmapped <> 0
and
ts.online$
in
(1,4)
and
ts.contents$ = 0
union
all
select
/*+ ordered use_nl(u) use_nl(fi) */
ts.
name
, fi.file#, u.ktfbuebno,
u.ktfbueblks * ts.blocksize, u.ktfbueblks, u.ktfbuefno
from
sys.recyclebin$ rb, sys.ts$ ts, sys.x$ktfbue u, sys.file$ fi
where
ts.ts# = rb.ts#
and
rb.ts# = fi.ts#
and
u.ktfbuefno = fi.relfile#
and
u.ktfbuesegtsn = rb.ts#
and
u.ktfbuesegfno = rb.file#
and
u.ktfbuesegbno = rb.block#
and
ts.bitmapped <> 0
and
ts.online$
in
(1,4)
and
ts.contents$ = 0
union
all
select
ts.
name
, fi.file#, u.block#,
u.length * ts.blocksize, u.length, u.file#
from
sys.ts$ ts, sys.uet$ u, sys.file$ fi, sys.recyclebin$ rb
where
ts.ts# = u.ts#
and
u.ts# = fi.ts#
and
u.segfile# = fi.relfile#
and
u.ts# = rb.ts#
and
u.segfile# = rb.file#
and
u.segblock# = rb.block#
and
ts.bitmapped = 0
/
ORACLE 11g中DBA_FREE_SPACE的定义:
create
or
replace
view
DBA_FREE_SPACE
(TABLESPACE_NAME, FILE_ID, BLOCK_ID,
BYTES, BLOCKS, RELATIVE_FNO)
as
select
ts.
name
, fi.file#, f.block#,
f.length * ts.blocksize, f.length, f.file#
from
sys.ts$ ts, sys.fet$ f, sys.file$ fi
where
ts.ts# = f.ts#
and
f.ts# = fi.ts#
and
f.file# = fi.relfile#
and
ts.bitmapped = 0
union
all
select
/*+ ordered use_nl(f) use_nl(fi) */
ts.
name
, fi.file#, f.ktfbfebno,
f.ktfbfeblks * ts.blocksize, f.ktfbfeblks, f.ktfbfefno
from
sys.ts$ ts, sys.x$ktfbfe f, sys.file$ fi
where
ts.ts# = f.ktfbfetsn
and
f.ktfbfetsn = fi.ts#
and
f.ktfbfefno = fi.relfile#
and
ts.bitmapped <> 0
and
ts.online$
in
(1,4)
and
ts.contents$ = 0
union
all
select
/*+ ordered use_nl(u) use_nl(fi) */
ts.
name
, fi.file#, u.ktfbuebno,
u.ktfbueblks * ts.blocksize, u.ktfbueblks, u.ktfbuefno
from
sys.recyclebin$ rb, sys.ts$ ts, sys.x$ktfbue u, sys.file$ fi
where
ts.ts# = rb.ts#
and
rb.ts# = fi.ts#
and
u.ktfbuefno = fi.relfile#
and
u.ktfbuesegtsn = rb.ts#
and
u.ktfbuesegfno = rb.file#
and
u.ktfbuesegbno = rb.block#
and
ts.bitmapped <> 0
and
ts.online$
in
(1,4)
and
ts.contents$ = 0
union
all
select
ts.
name
, fi.file#, u.block#,
u.length * ts.blocksize, u.length, u.file#
from
sys.ts$ ts, sys.uet$ u, sys.file$ fi, sys.recyclebin$ rb
where
ts.ts# = u.ts#
and
u.ts# = fi.ts#
and
u.segfile# = fi.relfile#
and
u.ts# = rb.ts#
and
u.segfile# = rb.file#
and
u.segblock# = rb.block#
and
ts.bitmapped = 0
/
|
那么在DBA_FREE_SPACE中找到的最大空闲块是否很有可能就是回收站中曾经的一个对象呢?那么我们来测试看看.
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SQL> show parameter recyclebin;
NAME
TYPE VALUE
------------------------------------ ----------- ------------------------------
recyclebin string
on
SQL>
CREATE
TABLE
ESCMOWNER.TTT
2
AS
3
SELECT
*
FROM
DBA_OBJECTS;
Table
created.
SQL> COL OWNER
FOR
A12;
SQL> COL SEGMENT_NAME
FOR
A32;
SQL>
SELECT
OWNER,SEGMENT_NAME, HEADER_FILE, HEADER_BLOCK
2
FROM
DBA_SEGMENTS
3
WHERE
OWNER=
'ESCMOWNER'
AND
SEGMENT_NAME=
'TTT'
;
OWNER SEGMENT_NAME HEADER_FILE HEADER_BLOCK
------------ -------------------------------- ----------- ------------
ESCMOWNER TTT 97 113025
SQL>
SQL>
SELECT
*
FROM
X$KTFBFE
WHERE
KTFBFEFNO=97;
ADDR INDX INST_ID KTFBFETSN KTFBFEFNO KTFBFEBNO KTFBFEBLKS
---------------- ---------- ---------- ---------- ---------- ---------- ----------
00007F57B2388CA0 222 1 9 97 524169 120
SQL>
DROP
TABLE
ESCMOWNER.TTT;
Table
dropped.
SQL> COL ORIGINAL_NAME
FOR
A16;
SQL>
SELECT
OBJ#,OWNER#,ORIGINAL_NAME,FILE#,BLOCK# ,FLAGS,
SPACE
FROM
RECYCLEBIN$;
OBJ# OWNER# ORIGINAL_NAME FILE# BLOCK# FLAGS
SPACE
---------- ---------- ---------------- ---------- ---------- ---------- ----------
805429 73 TTT 97 113025 30 896
SQL> PURGE DBA_RECYCLEBIN;
DBA Recyclebin purged.
SQL>
SELECT
*
FROM
X$KTFBFE
WHERE
KTFBFEFNO=97 ;
ADDR INDX INST_ID KTFBFETSN KTFBFEFNO KTFBFEBNO KTFBFEBLKS
---------------- ---------- ---------- ---------- ---------- ---------- ----------
00007F57B2388CA0 222 1 9 97 113025 8
00007F57B2388CA0 225 1 9 97 524169 120
SQL>
clip_image003
|
如上所示,清空回收站对象后,你会发现X$KTFBFE中多了一条记录,KTFBFEFNO 和 KTFBFEBNO分别为97 ,113025, 这个值显然就是删除对象TTT曾经的FILE_ID(97)和BLOCK_ID(113025)值.
另外,在测试过程中发现,并不是每次的测试结果都是在X$KTFBFE中多一条记录,有时候记录不会变化,但是X$KTFBFE中某条记录的KTFBFEBNO会变化,而这个变化跟清空回收站是有关系的。如下案例所示:
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SQL> show parameter recyclebin;
NAME
TYPE VALUE
------------------------------------ ----------- ------------------------------
recyclebin string
on
SQL>
CREATE
TABLE
TEST.TTT
2
AS
3
SELECT
*
FROM
DBA_OBJECTS;
Table
created.
SQL> COL OWNER
FOR
A12;
SQL> COL SEGMENT_NAME
FOR
A32;
SQL>
SELECT
OWNER,SEGMENT_NAME, HEADER_FILE, HEADER_BLOCK
2
FROM
DBA_SEGMENTS
3
WHERE
OWNER=
'TEST'
AND
SEGMENT_NAME=
'TTT'
;
OWNER SEGMENT_NAME HEADER_FILE HEADER_BLOCK
------------ -------------------------------- ----------- ------------
TEST TTT 5 130
SQL>
SELECT
*
FROM
X$KTFBFE
WHERE
KTFBFEFNO=5 ;
ADDR INDX INST_ID KTFBFETSN KTFBFEFNO KTFBFEBNO KTFBFEBLKS
---------------- ---------- ---------- ---------- ---------- ---------- ----------
00002BA829B19558 150 1 6 5 1280 506752
00002BA829B19558 151 1 6 5 508032 16256
SQL>
DROP
TABLE
TEST.TTT;
Table
dropped.
SQL>
SQL> COL ORIGINAL_NAME
FOR
A16;
SQL>
SELECT
OBJ#,OWNER#,ORIGINAL_NAME,FILE#,BLOCK# ,FLAGS,
SPACE
FROM
RECYCLEBIN$;
OBJ# OWNER# ORIGINAL_NAME FILE# BLOCK# FLAGS
SPACE
---------- ---------- ---------------- ---------- ---------- ---------- ----------
82820 85 TTT 5 130 30 1152
SQL>
SELECT
*
FROM
X$KTFBFE
WHERE
KTFBFEFNO=5 ;
ADDR INDX INST_ID KTFBFETSN KTFBFEFNO KTFBFEBNO KTFBFEBLKS
---------------- ---------- ---------- ---------- ---------- ---------- ----------
00002BA829B159D8 150 1 6 5 1280 506752
00002BA829B159D8 151 1 6 5 508032 16256
SQL> PURGE DBA_RECYCLEBIN;
DBA Recyclebin purged.
SQL>
SELECT
*
FROM
X$KTFBFE
WHERE
KTFBFEFNO=5 ;
ADDR INDX INST_ID KTFBFETSN KTFBFEFNO KTFBFEBNO KTFBFEBLKS
---------------- ---------- ---------- ---------- ---------- ---------- ----------
00002BA829B159D8 150 1 6 5 128 507904
00002BA829B159D8 151 1 6 5 508032 16256
SQL>
clip_image004
|
如上所示,在清空回收站的表以后,你查询X$KTFBFE,就会发现其中一条记录的KTFBFEBNO的变化了,它们的关系为 。
1280 -1152 = 128 。
所以,你会看到KTFBFEBNO的值从1280变为了128了。此时你查看DBA_FREE_SPACE,就会看到这样的情况。所以当清空回收站时,有可能是数据库将这个表的空间标记为了空闲块,也有可能是将这个空闲块合并到其它空闲块去了.
X$KTFBFE其实是这几个单词[k]ernel [t]ablespace [f]ile [b]itmapped [f]ree [e]xtents 的首字母。关于这个系统视图最深入的介绍,莫过于这篇文章谈谈Oracle dba_free_space,有兴趣可以验证、测试一下.
以上所述是小编给大家介绍的关于ORACLE通过file_id与block_id定位数据库对象遇到的问题引发的思考,希望对大家有所帮助,如果大家有任何疑问欢迎给我留言,小编会及时回复大家的! 。
原文链接:http://www.cnblogs.com/kerrycode/p/6576988.html 。
最后此篇关于关于ORACLE通过file_id与block_id定位数据库对象遇到的问题引发的思考的文章就讲到这里了,如果你想了解更多关于关于ORACLE通过file_id与block_id定位数据库对象遇到的问题引发的思考的内容请搜索CFSDN的文章或继续浏览相关文章,希望大家以后支持我的博客! 。
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