Oracle ASM 相关的视图(V$) 和数据字典（X$）

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ASM由于其高度的封装性，使得我们很难知道窥探其内部的原理。可以通过一下视图和数据字典来来查看ASM 的信息。

一. 相关视图和数据字典

View Name

X$ Table name

Description

V$ASM_DISKGROUP

X$KFGRP

performs disk discovery and lists diskgroups

V$ASM_DISKGROUP_STAT

X$KFGRP_STAT

diskgroup stats without disk discovery

V$ASM_DISK

X$KFDSK, X$KFKID

performs disk discovery, lists disks and their usage metrics

V$ASM_DISK_STAT

X$KFDSK_STAT, X$KFKID

lists disks and their usage metrics

V$ASM_FILE

X$KFFIL

lists ASM files, including metadata/asmdisk files

V$ASM_ALIAS

X$KFALS

lists ASM aliases, files and directories

V$ASM_TEMPLATE

X$KFTMTA

lists the available templates and their properties

V$ASM_CLIENT

X$KFNCL

lists DB instances connected to ASM

V$ASM_OPERATION

X$KFGMG

lists rebalancing operations

N.A.

X$KFKLIB

available libraries, includes asmlib path

N.A.

X$KFDPARTNER

lists disk-to-partner relationships

N.A.

X$KFFXP

extent map table for all ASM files

N.A.

X$KFDAT

extent list for all ASM disks

N.A.

X$KFBH

describes the ASM cache (buffer cache of ASM in blocks of 4K (_asm_blksize)

N.A.

X$KFCCE

a linked list of ASM blocks. to be further investigated

This list is obtained querying v$fixed_view_definitionwhere view_name like '%ASM%' which exposes all the v$ and gv$ views with theirdefinition. Fixed tables are exposed by querying v$fixed_table where name like'x$kf%' (ASM fixed tables use the 'X$KF' prefix).

SQL>select * fromv$fixed_view_definition whereview_name like '%ASM%';

SQL>select * from sys.v$fixed_tablewhere name like 'X$KF%' ;

Noteon 11g there are additional V$views: , and X$tables: *

New in 11g:

View Name

X$ Table name

Description

V$ASM_ATTRIBUTE

X$KFENV

ASM attributes, the X$ table shows also 'hidden' attributes

V$ASM_DISK_IOSTAT

X$KFNSDSKIOST

I/O statistics

N.A.

X$KFDFS

N.A.

X$KFDDD

N.A.

X$KFGBRB

N.A.

X$KFMDGRP

N.A.

X$KFCLLE

N.A.

X$KFVOL

N.A.

X$KFVOLSTAT

N.A.

X$KFVOFS

N.A.

X$KFVOFSV

二. Striping and Mirroring with ASM, extentsand allocation units

Abasic example, using ASM and normal redundancy: the available storage, say 64HDs over FC SAN, are used to create the main DB diskgroup: DATADG. DATADG islogically divided into 2 evenly sized groups of disks: 32 disks in failgroupN.1 and 32 in failgroup N.2. Oracle datafiles created in DATADG are 'striped'into smaller pieces, extents of 1MB in size. Extents are allocated to thestorage in 2 (mirrored) allocation units (AU): one AU in failgroup N.1 theother in failgroup N.2.

Allocation Units

EveryASM disk is divided into allocation units (AU). An AU is the fundamental unitof allocation within a disk group. A file extent consists of one or more AU. AnASM file consists of one or more file extents.

When you create a disk group, youcan set the ASM AU size to be between 1 MB and 64 MB in powers of two, such as,1, 2, 4, 8, 16, 32, or 64. Larger AU sizes typically provide performanceadvantages for data warehouse applications that use large sequential reads.

默认的AU 大小是1M。

三. X$KFFXP

ThisX$ table contains the mapping between files, extents and allocation units. Itallows to track the position of all the extents of a given file striped andmirrored across storage.

Note:RDBMS read operations access only the primary extent of a mirrored couple(unless there is an IO error) . Write operations instead write all mirroredextents to disk.

X$KFFXP Column Name

Description

ADDR

x$ table address/identifier

INDX

row unique identifier

INST_ID

instance number (RAC)

NUMBER_KFFXP

ASM file number. Join with v$asm_file and v$asm_alias

COMPOUND_KFFXP

File identifier. Join with compound_index in v$asm_file

INCARN_KFFXP

File incarnation id. Join with incarnation in v$asm_file

PXN_KFFXP

Progressive file extent number

XNUM_KFFXP

ASM file extent number (mirrored extent pairs have the same extent value)

GROUP_KFFXP

ASM disk group number. Join with v$asm_disk and v$asm_diskgroup

DISK_KFFXP

Disk number where the extent is allocated. Join with v$asm_disk

AU_KFFXP

Relative position of the allocation unit from the beginning of the disk. The allocation unit size (1 MB) in v$asm_diskgroup

LXN_KFFXP

0->primary extent, ->mirror extent, 2->2nd mirror copy (high redundancy and metadata)

FLAGS_KFFXP

N.K.

CHK_KFFXP

N.K.

SIZE_KFFXP

11g, to support variable size AU, integer value which marks the size of the extent in AU size units.

Example1 - reading ASM files with direct OS access

（1）Find the 2 mirrored extents of an ASM file (thespfile in this example)

sys@+ASM1>selectGROUP_KFFXP,DISK_KFFXP,AU_KFFXP from x$kffxp where number_kffxp=(selectfile_number from v$asm_alias where name='spfiletest1.ora');

GROUP_KFFXP DISK_KFFXP AU_KFFXP

----------- ---------- ----------

1 20 379

1 3 101

（2）find the diskname

sys@+ASM1> select disk_number,path fromv$asm_disk where GROUP_NUMBER=1 anddisk_number in (3,20);

DISK_NUMBER PATH

---------------------------------------------------

3 /dev/mpath/itstor417_2p1

20 /dev/mpath/itstor419_2p1

（3）access the data directly from disk with dd

ddif=/dev/mpath/itstor417_2p1 bs=1024k count=1 skip=101|strings|more

四. X$KFDAT

This X$ table contains details of all allocation units (free and used).

X$KFDAT Column Name

Description

ADDR

x$ table address/identifier

INDX

row unique identifier

INST_ID

instance number (RAC)

GROUP_KFDAT

diskgroup number, join with v$asm_diskgroup

NUMBER_KFDAT

disk number, join with v$asm_disk

COMPOUND_KFDAT

disk compund_index, join with v$asm_disk

AUNUM_KFDAT

Disk allocation unit (relative position from the beginning of the disk), join with x$kffxp.au_kffxp

V_KFDAT

V=this Allocation Unit is used; F=AU is free

FNUM_KFDAT

file number, join with v$asm_file

I_KFDAT

N.K.

XNUM_KFDAT

Progressive file extent number join with x$kffxp.pxn_kffxp

RAW_KFDAT

raw format encoding of the disk,and file extent information

Example2 - listallocation units of a given file from x$kfdat

similarly to example 1 above, another wayto retrieve ASM file allocation maps:

sys@+ASM1> selectGROUP_KFDAT,NUMBER_KFDAT,AUNUM_KFDAT from x$kfdat where fnum_kfdat=(selectfile_number from v$asm_alias where name='spfiletest1.ora');

GROUP_KFDAT NUMBER_KFDAT AUNUM_KFDAT

----------- ------------ -----------

1 3 101

1 20 379

Example3 - from strace data of an oracle userprocess

（1）from the strace file of a user(shadow) process identify IO operations:

ex: strace-p 30094 2>&1|grep -v time

read64(15,"#\242\0\0\33\0@\2\343\332\177\303s\5\1\4\211\330\0\0\0"..., 8192,473128960) = 8192

itis a read operation of 8KB (oracle block) at the offset 473128960 (=451 MB +27*8KB) from file descriptor FD=15

（2）using /proc/30094/fd -> findFD=15 is /dev/mpath/itstor420_1p1

（3）I find the group and disk number ofthe file:

sys@+ASM1> selectGROUP_NUMBER,DISK_NUMBER from v$asm_disk

where path='/dev/mpath/itstor420_1p1';

GROUP_NUMBER DISK_NUMBER

------------ -----------

1 30

（4）using the disk number, group numberand offset (from strace above) I find the file number and extent number:

sys@+ASM1> select number_kffxp,XNUM_KFFXP from x$kffxp where group_kffxp=1 and disk_kffxp=20 and au_kffxp=451;

NUMBER_KFFXP XNUM_KFFXP

------------ ----------

268 17

（5）from v$asm_file fnum=268 is file ofthe users' tablesspace:

sys@+ASM1> select name from v$asm_aliaswhere FILE_NUMBER=268

NAME

------------------------------

USERS.268.612033477

sys@DB> select file#,name fromv$datafile where upper(name) like '%USERS.268.612033477';

FILE# NAME

------------------------------------------------------------------

9 +TEST1_DATADG1/test1/datafile/users.268.612033477

（6）from dba extents finally find theowner and segment name relative to the original IO operation:

sys@TEST1> selectowner,segment_name,segment_type from dba_extents

where FILE_ID=9 and 27+17*1024*1024 betweenblock_id and block_id+blocks;

OWNER SEGMENT_NAME SEGMENT_TYPE

------------------------------------------------------------ ------------------

SCOTT EMP TABLE

五. X$KFDPARTNER

ThisX$ table contains the disk-to-partner (1-N) relationship. Two disks of a givenASM diskgroup are partners if they each contain a mirror copy of the sameextent. Therefore partners must belong to different failgroups of the samediskgroup. From a few liveexamples I can see that typically disks have 10 partners each atdiskgroup creation and fluctuate around 10 partners following ASM operations.This mechanism is in place to reduce the chance of losing both sides of themirror in case of double disk failure.

X$KFDPARTNER Column Name

Description

ADDR

x$ table address/identifier

INDX

row unique identifier

INST_ID

instance number (RAC)

GRP

diskgroup number, join with v$asm_diskgroup

DISK

disk number, join with v$asm_disk

COMPOUND

disk identifier. Join with compound_index in v$asm_disk

NUMBER_KFDPARTNER

partner disk number, i.e. disk-to-partner (1-N) relationship

MIRROR_KFDPARNER

=1 in a healthy normal redundancy config

PARITY_KFDPARNER

=1 in a healthy normal redundancy config

ACTIVE_KFDPARNER

=1 in a healthy normal redundancy config

六. X$KFFIL and metadata files

Three types of metadata:

（1）diskgroup metadata: files with NUMBER_KFFIL <256 ASM metadata andASMlog files. These files have high redundancy (3 copies) and block size =4KB.

1）ASM log files are used for ASMinstance and crash recovery when a crash happens with metadata operations (seebelow COD and ACD)

2）at diskgroup creation 6 files withmetadata are visible from x$kffil

（2）disk metadata: disk headers (typically the first 2 AU of each disk)are not listed in x$kffil (they appear as file number 0 in x$kfdat). Containdisk membership information. This part of the disk has to be 'zeroed out'before the disk can be added to ASM diskgroup as a new disk.

（3）file metadata: 3 mirrored extents with file metadata, visible fromx$kffxp and x$kfdat

Example: list all files,system and users' with their sizes:

SYS@+ASM2(rac2)> select group_kffil group#,number_kffil file#, filsiz_kffil filesize_after_mirr, filspc_kffilraw_file_size from x$kffil;

GROUP# FILE# FILESIZE_AFTER_MIRRRAW_FILE_SIZE

---------- ---------- --------------------------------

1 1 2097152 2097152

1 2 1048576 1048576

1 3 88080384 89128960

1 4 1392640 2097152

1 5 1048576 1048576

1 6 1048576 1048576

1 256 545267712 547356672

1 257 629153792 631242752

1 258 351281152 353370112

1 259 7872512 8388608

1 260 15319040 16777216

Example: List all filesincluding metadata allocated in the ASM diskgroups

SYS@+ASM2(rac2)> select group_kfdat group#,FNUM_KFDAT file#, sum(1) AU_used from x$kfdat where v_kfdat='V' group by group_kfdat,FNUM_KFDAT,v_kfdat;

GROUP# FILE# AU_USED

---------- ---------- ----------

1 0 2

1 1 2

1 2 1

1 3 85

1 4 2

1 5 1

1 6 1

1 256 522

1 257 602

1 258 337

1 259 8

Descriptionof metadata files

This paragraph is from: Oracle AutomaticStorage Management, Oracle Press Nov 2007, N. Vengurlekar, M. Vallath, R.Long

（1）. File#0, AU=0: disk header (disk name, etc), Allocation Table (AT)and Free Space Table (FST)

（2）. File#0, AU=1: Partner Status Table (PST)

（3）. File#1: File Directory (files and their extent pointers)

（4）. File#2: Disk Directory

（5）. File#3: Active Change Directory (ACD) The ACD is analogous to a redolog, where changes to the metadata are logged. Size=42MB * number of instances

（6）. File#4: Continuing Operation Directory (COD). The COD is analogousto an undo tablespace. It maintains the state of active ASM operations such asdisk or datafile drop/add. The COD log record is either committed or rolledback based on the success of the operation.

（7）. File#5: Template directory

（8）. File#6: Alias directory

（9）. 11g, File#9: Attribute Directory

（10）. 11g, File#12: Stalenessregistry, created when needed to track offline disks

七. DBMS_DISKGROUP, an internal ASM package

dbms_diskgroupis an Oracle 'internal package' (it doesn't show up as an object being that ASMhas no dictionary) called dbms_diskgroup. It is used to access the ASM withfilesystem-like calls. 11g asmcmd uses this package to implement the cpcommand. A list of procedures:

dbms_diskgroup.open(:fileName, :openMode, :fileType, :blkSz, :hdl,:plkSz, :fileSz)

dbms_diskgroup.createfile(:fileName, :fileType, :blkSz, :fileSz, :hdl, :plkSz, :fileGenName)

dbms_diskgroup.close(:hdl)

dbms_diskgroup.read(:hdl, :offset, :blkSz, :data_buf)

dbms_diskgroup.commitfile(:handle)

dbms_diskgroup.resizefile(:handle,:fsz)

dbms_diskgroup.remap(:gnum, :fnum, :virt_extent_num)

dbms_diskgroup.getfileattr(:fileName, :fileType, :fileSz, :blkSz)

dbms_diskgroup.checkfile(?)

dbms_diskgroup.patchfile(?)

八. ASM parameters and underscore parameters

可以使用SQL 查看ASM 参数：

/* Formatted on 2011/8/30 16:28:54(QP5 v5.163.1008.3004) */

SELECT a.ksppinm"Parameter", c.ksppstvl"Instance Value"

FROMx$ksppi a,x$ksppcv b,x$ksppsv c

WHERE a.indx = b.indx AND a.indx = c.indx ANDksppinm LIKE '%asm%'

ORDER BY a.ksppinm;

或者：

select * fromall_parameters where name like '%asm%';

Oracle all_parameters 视图

http://blog.csdn.net/xujinyang/article/details/6823063

Parameter Name

Value

_asm_acd_chunks

_asm_allow_only_raw_disks

TRUE

_asm_allow_resilver_corruption

FALSE

_asm_ausize

1048576

_asm_blksize

4096

_asm_disk_repair_time

14400

_asm_droptimeout

_asm_emulmax

10000

_asm_emultimeout

_asm_kfdpevent

_asm_libraries

ufs (may differ if asmlib is used)

_asm_maxio

1048576

_asm_stripesize

131072

_asm_stripewidth

_asm_wait_time

_asmlib_test

_asmsid

asm

asm_diskgroups

list of diskgroups to be mounted at startup

asm_diskstring

search path for physical disks to be used with ASM

asm_power_limit

default rebalance power value

注意这里的_asm_ausize =1M

Oracle 11g 里新增加的参数：

Parameter Name

Value

_asm_compatibility

10.1

_asm_dbmsdg_nohdrchk

FALSE

_asm_droptimeout

removed in 11g

_asm_kfioevent

_asm_repairquantum

_asm_runtime_capability_volume_support

FALSE

_asm_skip_resize_check

FALSE

_lm_asm_enq_hashing

TRUE

asm_preferred_read_failure_groups

九. ASM-related acronyms 相关名词解释

（1）. PST - Partner Status Table. Maintains info on disk-to-diskgroupmembership.

（2）. COD - Continuing Operation Directory. The COD structuremaintains the state of active ASM operations or changes, such as disk ordatafile drop/add. The COD log record is either committed or rolled back basedon the success of the operation. (source Oracle whitepaper)

（3）. ACD - Active Change Directory. The ACD is analogous to a redolog, where changes to the metadata are logged. The ACD log record is used todetermine point of recovery in the case of ASM operation failures or instancefailures. (source Oracle whitepaper)

（4）. OSM Oracle Storage Manager, legacy name, synonymous of ASM

（5）. CSS Cluster Synchronization Services. Part of Oracleclusterware, mandatory with ASM even in single instance. CSS is used toheartbeat the health of the ASM instances.

（6）. RBAL - Oracle backgroud process. In an ASM instance coordinatedrebalancing operations. In a DB instance, opens and mount diskgroups from thelocal ASM instance.

（7）. ARBx - Oracle backgroud processes. In an ASM instance, a slavefor rebalancing operations

（8）. PSPx - Oracle backgroud processes. In an ASM instance, ProcessSpawners

（9）. GMON - Oracle backgroud processes. In an ASM instance,diskgroup monitor.

（10）. ASMB - Oracle backgroudprocess. In an DB instance, keeps a (bequeath) persistent DB connection to thelocal ASM instance. Provides hearthbeat and ASM statistics. During a diskgrouprebalancing operation ASM communicates to the DB AU changes via this connection.

（11）. O00x - Oracle backgroudprocesses. Slaves used to connected from the DB to the ASM instance for 'shortoperations'.

Oracle ASM 相关的 视图(V$) 和 数据字典（X$）

一. 相关视图和数据字典

二. Striping and Mirroring with ASM, extentsand allocation units

三. X$KFFXP

四. X$KFDAT

五. X$KFDPARTNER

六. X$KFFIL and metadata files

Descriptionof metadata files

七. DBMS_DISKGROUP, an internal ASM package

八. ASM parameters and underscore parameters

九. ASM-related acronyms 相关名词解释

Oracle ASM 相关的视图(V$) 和数据字典（X$）