X$KFFXP是ASM(Automatic Storage Management)自动存储管理特性的重要内部视图，该视图反应了File Extent Map映射关系，ASM会将文件split成多个多个piece分片，这些分片被称为Extents。 在Disk上存放这些Extent的位置，就是我们常说的”Allocation Unit”。
KFF意为Kernel File，X$KFFXP即Kernel File Extent Maps， 该内部视图的一条记录代表一个Extent。
其字段含义如下：
GROUP_KFFXP diskgroup number (1 - 63) ASM disk group number. Join with v$asm_disk and v$asm_diskgroup NUMBER_KFFXP file number for the extent ASM file number. Join with v$asm_file and v$asm_alias COMPOUND_KFFXP (group_kffxp << 24) + file # File identifier. Join with compound_index in v$asm_file INCARN_KFFXP file incarnation number File incarnation id. Join with incarnation in v$asm_file PXN_KFFXP physical extent number Extent number per file XNUM_KFFXP extent number bit 31 set if indirect Logical extent number per file (mirrored extents have the same value) LXN_KFFXP logical extent number 0,1 used to identify primary/mirror extent, 2 identifies file header allocation unit (hypothesis) used in the query such that we go after only the primary extents, not secondary extents DISK_KFFXP disk on which AU is located Disk number where the extent is allocated. Join with v$asm_disk Relative position of the allocation unit from the beginning of the disk. AU_KFFXP AU number on disk of AU allocation unit size (1 MB) in v$asm_diskgroup 从11g开始加入了CHK_KFFXP SIZE_KFFXP 2个新的字段 CHK_KFFXP 未知 可能是范围为[0-256]的某种校验值 SIZE_KFFXP size_kffxp is used such that we account for variable sized extents. sum(size_kffxp) provides the number of AUs that are on that disk.
在实例级别控制ASM Diskgroup AU 和 stripe size的是2个隐藏参数 _asm_ausize 1048576 以及 _asm_stripesize 131072。从11g开始一个Extent可能包含多个AU。
可以通过以下脚本查询文件与Extent等ASM属性的映射关系:
set linesize 140 pagesize 1400 col "FILE NAME" format a40 set head on select NAME "FILE NAME", NUMBER_KFFXP "FILE NUMBER", XNUM_KFFXP "EXTENT NUMBER", DISK_KFFXP "DISK NUMBER", AU_KFFXP "AU NUMBER", SIZE_KFFXP "NUMBER of AUs" from x$kffxp, v$asm_alias where GROUP_KFFXP = GROUP_NUMBER and NUMBER_KFFXP = FILE_NUMBER and system_created = 'Y' and lxn_kffxp = 0 order by name;
SQL> select s.name,STRIPED 2 from v$asm_file a, v$asm_alias s 3 where a.GROUP_NUMBER = s.GROUP_NUMBER 4 and a.FILE_NUMBER = s.FILE_NUMBER 5 and STRIPED = 'FINE' 6 / NAME STRIPE ---------------------------------------------------------------------- ------ Backup.263.769482651 FINE Current.260.766620025 FINE Current.261.766620025 FINE Backup.481.769484083 FINE SQL> set linesize 140 pagesize 1400 SQL> col "FILE NAME" format a40 SQL> set head on SQL> select NAME "FILE NAME", 2 NUMBER_KFFXP "FILE NUMBER", 3 XNUM_KFFXP "EXTENT NUMBER", 4 DISK_KFFXP "DISK NUMBER", 5 AU_KFFXP "AU NUMBER" 6 from x$kffxp, v$asm_alias 7 where GROUP_KFFXP = GROUP_NUMBER 8 and NUMBER_KFFXP = FILE_NUMBER 9 and name in ('Backup.263.769482651', 10 'Current.260.766620025', 11 'Current.261.766620025', 12 'Backup.481.769484083') 13 order by DISK_KFFXP,AU_KFFXP; FILE NAME FILE NUMBER EXTENT NUMBER DISK NUMBER AU NUMBER ---------------------------------------- ----------- ------------- ----------- ---------- Backup.263.769482651 263 1 0 416 Backup.263.769482651 263 11 0 417 Backup.263.769482651 263 20 0 418 Current.261.766620025 261 1 0 625 Current.261.766620025 261 4 0 626 Current.261.766620025 261 6 0 627 Current.261.766620025 261 8 0 628 Current.261.766620025 261 10 0 629 Current.261.766620025 261 12 0 630 Current.261.766620025 261 14 0 631 Current.261.766620025 261 16 0 632 Current.261.766620025 261 18 0 633 Current.261.766620025 261 21 0 634 Current.261.766620025 261 23 0 635 Current.260.766620025 260 1 0 636 Current.260.766620025 260 4 0 637 Current.260.766620025 260 6 0 638 Current.260.766620025 260 8 0 639 Current.260.766620025 260 10 0 640 Current.260.766620025 260 12 0 641 Current.260.766620025 260 14 0 642 Current.260.766620025 260 16 0 643 Current.260.766620025 260 18 0 644 Current.260.766620025 260 21 0 645 Current.260.766620025 260 23 0 646 Backup.481.769484083 481 0 0 10715 Backup.481.769484083 481 3 0 10716 Backup.481.769484083 481 5 0 10717 Backup.481.769484083 481 7 0 10718 Backup.481.769484083 481 9 0 10719 Backup.481.769484083 481 11 0 10720 Backup.481.769484083 481 13 0 10721 Backup.481.769484083 481 15 0 10722 Backup.481.769484083 481 17 0 10723 Backup.481.769484083 481 20 0 10724 Backup.481.769484083 481 22 0 10725 Current.261.766620025 261 0 1 626 Current.261.766620025 261 3 1 627 Current.261.766620025 261 5 1 628 Current.261.766620025 261 7 1 629 Current.261.766620025 261 9 1 630 Current.261.766620025 261 11 1 631 Current.261.766620025 261 13 1 632 Current.261.766620025 261 15 1 633 Current.261.766620025 261 17 1 634 Current.261.766620025 261 19 1 635 Current.261.766620025 261 22 1 636 Current.260.766620025 260 0 1 637 Current.260.766620025 260 3 1 638 Current.260.766620025 260 5 1 639 Current.260.766620025 260 7 1 640 Current.260.766620025 260 9 1 641 Current.260.766620025 260 11 1 642 Current.260.766620025 260 13 1 643 Current.260.766620025 260 15 1 644 Current.260.766620025 260 17 1 645 Current.260.766620025 260 19 1 646 Current.260.766620025 260 22 1 647 Backup.263.769482651 263 0 1 3333 Backup.263.769482651 263 2 1 3334 Backup.263.769482651 263 3 1 3335 Backup.263.769482651 263 4 1 3336 Backup.263.769482651 263 5 1 3337 Backup.263.769482651 263 6 1 3338 Backup.263.769482651 263 7 1 3339 Backup.263.769482651 263 8 1 3340 Backup.263.769482651 263 9 1 3341 Backup.263.769482651 263 10 1 3342 Backup.263.769482651 263 12 1 3343 Backup.263.769482651 263 13 1 3344 Backup.263.769482651 263 14 1 3345 Backup.263.769482651 263 15 1 3346 Backup.263.769482651 263 16 1 3347 Backup.263.769482651 263 17 1 3348 Backup.263.769482651 263 18 1 3349 Backup.263.769482651 263 19 1 3350 Backup.263.769482651 263 21 1 3351 Backup.263.769482651 263 22 1 3352 Backup.263.769482651 263 23 1 3353 Backup.481.769484083 481 1 1 10727 Backup.481.769484083 481 4 1 10728 Backup.481.769484083 481 6 1 10729 Backup.481.769484083 481 8 1 10730 Backup.481.769484083 481 10 1 10731 Backup.481.769484083 481 12 1 10732 Backup.481.769484083 481 14 1 10733 Backup.481.769484083 481 16 1 10734 Backup.481.769484083 481 18 1 10735 Backup.481.769484083 481 21 1 10736 Backup.481.769484083 481 23 1 10737 Current.261.766620025 261 2 2 81 Current.261.766620025 261 20 2 82 Current.260.766620025 260 2 2 83 Current.260.766620025 260 20 2 84 Backup.481.769484083 481 2 2 1362 Backup.481.769484083 481 19 2 1363 96 rows selected. 1 select NAME "FILE NAME", 2 NUMBER_KFFXP "FILE NUMBER", 3 PXN_KFFXP, 4 XNUM_KFFXP "EXTENT NUMBER", 5 DISK_KFFXP "DISK NUMBER", 6 AU_KFFXP "AU NUMBER", 7 SIZE_KFFXP 8 from x$kffxp, v$asm_alias 9 where GROUP_KFFXP = GROUP_NUMBER 10 and NUMBER_KFFXP = FILE_NUMBER 11 and name ='Current.260.766620025' 12* order by XNUM_KFFXP,DISK_KFFXP, AU_KFFXP SQL> / FILE NAME FILE NUMBER PXN_KFFXP EXTENT NUMBER DISK NUMBER AU NUMBER SIZE_KFFXP ---------------------------------------- ----------- ---------- ------------- ----------- ---------- ---------- Current.260.766620025 260 0 0 1 637 1 Current.260.766620025 260 1 1 0 636 1 Current.260.766620025 260 2 2 2 83 1 Current.260.766620025 260 3 3 1 638 1 Current.260.766620025 260 4 4 0 637 1 Current.260.766620025 260 5 5 1 639 1 Current.260.766620025 260 6 6 0 638 1 Current.260.766620025 260 7 7 1 640 1 Current.260.766620025 260 8 8 0 639 1 Current.260.766620025 260 9 9 1 641 1 Current.260.766620025 260 10 10 0 640 1 Current.260.766620025 260 11 11 1 642 1 Current.260.766620025 260 12 12 0 641 1 Current.260.766620025 260 13 13 1 643 1 Current.260.766620025 260 14 14 0 642 1 Current.260.766620025 260 15 15 1 644 1 Current.260.766620025 260 16 16 0 643 1 Current.260.766620025 260 17 17 1 645 1 Current.260.766620025 260 18 18 0 644 1 Current.260.766620025 260 19 19 1 646 1 Current.260.766620025 260 20 20 2 84 1 Current.260.766620025 260 21 21 0 645 1 Current.260.766620025 260 22 22 1 647 1 Current.260.766620025 260 23 23 0 646 1 24 rows selected.请问下我在11gR2版为什么查不到此视图啊？
SQL> show user;
USER is “SYS”
SQL> select * from x$kffxp;
no rows selected
SQL> select name from v$datafile;
NAME
——————————————————————————–
+DATA/testdb/datafile/system.263.784600547
+DATA/testdb/datafile/sysaux.262.784600547
+DATA/testdb/datafile/undotbs1.261.784600547
+DATA/testdb/datafile/users.259.784600547
+DATA/testdb/test/tbs01.dbf
SQL> desc x$kffxp;
Name Null? Type
—————————————– ——– —————————-
ADDR RAW(4)
INDX NUMBER
INST_ID NUMBER
GROUP_KFFXP NUMBER
NUMBER_KFFXP NUMBER
COMPOUND_KFFXP NUMBER
INCARN_KFFXP NUMBER
PXN_KFFXP NUMBER
XNUM_KFFXP NUMBER
LXN_KFFXP NUMBER
DISK_KFFXP NUMBER
AU_KFFXP NUMBER
FLAGS_KFFXP NUMBER
CHK_KFFXP NUMBER
SIZE_KFFXP NUMBER
SQL> select * from x$kffxp;
no rows selected
不好意思 说错了 是查不到任何东西出来？
这是一个ASM type instance 的视图，不要在instance_type=RDBMS的实例中查询它。
[grid@test01 admin]$ sqlplus / as sysasm
SQL*Plus: Release 11.2.0.1.0 Production on Fri Jun 29 11:39:52 2012
Copyright (c) 1982, 2009, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 – Production
With the Automatic Storage Management option
SQL> select instance_name,status from v$instance;
INSTANCE_NAME STATUS
—————- ————
+ASM STARTED
嗯，换了实例可以查询了，TKS。
不过还请教一个问题，asm实例的状态为started，我在远程client应该怎么连上去呢？ （好像见过10G可以）
我有一个疑问想请教一下。
确实像你说的那样，从11g开始，oracle支持Variable-Size Extents，在他的官方文档中如是描述：
The extent size of a file varies as follows:
•Extent size always equals the disk group AU size for the first 20000 extent sets (0 – 19999).
•Extent size equals 4*AU size for the next 20000 extent sets (20000 – 39999).
•Extent size equals 16*AU size for the next 20000 and higher extent sets (40000+).
也就是文件的extent编号超过20000，每个extent就会有4AU，
extent编号超过40000，每个extent就会有16AU。
这样的好处当然是可以减小维护extent map所占用的空间。
但是现在让我比较崩溃的是，在我自己的一个11gR2的RAC环境上，我查询出来却貌似不是oracle文档中说的这样。
我用的查询是在你的查询基础上修改了一点点：
SQL> select * from (select NAME “FILE NAME”,
NUMBER_KFFXP “FILE NUMBER”,
XNUM_KFFXP “EXTENT NUMBER”,
DISK_KFFXP “DISK NUMBER”,
AU_KFFXP “AU NUMBER”,
SIZE_KFFXP “NUMBER of AUs”
from x$kffxp, v$asm_alias
where GROUP_KFFXP = GROUP_NUMBER
and NUMBER_KFFXP = FILE_NUMBER
and system_created = ‘Y’
and lxn_kffxp = 0
and NUMBER_KFFXP=293
and XNUM_KFFXP != 2147483648
order by AU_KFFXP desc) where rownum < 10; 2 3 4 5 6 7 8 9 10 11 12 13 14
FILE NAME FILE NUMBER EXTENT NUMBER DISK NUMBER AU NUMBER NUMBER of AUs
———————— ———– ————- ———– ———- ————-
TPCH1T.293.811454469 293 72638 3 20412 1
TPCH1T.293.811454469 293 72639 8 20412 1
TPCH1T.293.811454469 293 72628 3 20411 1
TPCH1T.293.811454469 293 72634 5 20411 1
TPCH1T.293.811454469 293 72629 8 20411 1
TPCH1T.293.811454469 293 72618 3 20410 1
TPCH1T.293.811454469 293 72624 5 20410 1
TPCH1T.293.811454469 293 72619 8 20410 1
TPCH1T.293.811454469 293 72608 3 20409 1
9 rows selected.
可以看到Extent Number都已经7、8万了，但是AUs仍然是1，并没有像oracle文档中说的那样变为16AU。
所以不知道这是怎么回事啊？
11.2.0.4 for OEL 6.3 RAC 查询ASM实例的x$kffxp ，是没有数据的，换成其它表了吗？
补充：在+ASM1上可以查到数据，+ASM2实例上没有数据
抱歉，刚才发现crs不正常(CRS-0184)，但ASM和db都是正常的，重新启动后CRS正常，可以在2号节点上查询到x$kffxp数据了
This feature is automatic for newly created and resized datafiles when the disk group compatibility attributes are set to Oracle Release 11 or higher.