Oracle ASM Metadata Disk Utility (AMDU): View the metadata/content of asm diskgroups without mounting them

Hi,

When the ASM Diskgroups are mounted and the ASM instance is up and running you can view various dynamic views such as v$asm_diskgroup, v$asm_disk, v$asm_template etc to view the disk properties.

But, When the diskgroup is not mounted, this information is not available, which makes difficult to diagnose the errors avoiding the diskgroup to be mounted. Especially in scenarious like disk header issues, This problem has been resolved with AMDU.

ASM Metadata Disk utility (AMDU) is a tool introduced in 11g where it is posible to extract all the available metadata from one or more ASM disks, generate formatted block printouts from the dump output, extract one or more files from a diskgroup (mounted/unmounted) and write them to the OS file system.

Although this tool was released with 11g, it can be used with ASM 10g. by Placing the files into 10g home.

Download the AMDU Utility from ID 553639.1 as per your platform, and extract this will place a amdu binary and some lib files in the present working directory.

Set you LD_LIBRARY_PATH and the run AMDU utility.

$cd
$export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`pwd`
or $setenv LD_LIBRARY_PATH ${LD_LIBRARY_PATH}:`pwd`
$export PATH=$PATH:`pwd` or setenv PATH ${PATH}:`pwd`

or

$cd
$export LIBPATH=$LIBPATH:`pwd`
or $setenv LIBPATH ${LIBPATH}:`pwd`
$export PATH=$PATH:`pwd` or setenv PATH ${PATH}:`pwd`

Running the AMDU Script:-

amdu -diskstring '/dev/asm1_disk*' -dump 'DATA1'

Three files will be created:

* report.txt which provides details of disks identified during the amdu execution

$ more report.txt
-*-amdu-*-
******************************* AMDU Settings ********************************
ORACLE_HOME = /u01/app/11.2.0/grid
System name: Linux
Node name:
Release: 2.6.18-128.4.1.0.1.el5
Version: #1 SMP Tue Aug 4 15:10:25 EDT 2009
Machine: i686
amdu run:
Endianess: 1
...
----------------------------- DISK REPORT N0001 ------------------------------
Disk Path: ORCL:DISK1
Unique Disk ID:
Disk Label: DISK1
Physical Sector Size: 512 bytes
Disk Size: 4886 megabytes
Group Name: DATA
Disk Name: DISK1
Failure Group Name: DISK1
Disk Number: 0
Header Status: 3
Disk Creation Time: 2010/03/01 15:07:47.135000
Last Mount Time: 2011/09/02 15:35:52.676000
Compatibility Version: 0x0b200000(11020000)
Disk Sector Size: 512 bytes
Disk size in AUs: 4886 AUs
Group Redundancy: 1
Metadata Block Size: 4096 bytes
AU Size: 1048576 bytes
Stride: 113792 AUs
Group Creation Time: 2010/03/01 15:07:46.819000
File 1 Block 1 location: AU 2
OCR Present: NO
...
************************** SCANNING DISKGROUP DATA ***************************
Creation Time: 2010/03/01 15:07:46.819000
Disks Discovered: 2
Redundancy: 1
AU Size: 1048576 bytes
Metadata Block Size: 4096 bytes
Physical Sector Size: 512 bytes
Metadata Stride: 113792 AU
Duplicate Disk Numbers: 0
---------------------------- SCANNING DISK N0001 -----------------------------
Disk N0001: 'ORCL:DISK1'
Allocated AU's: 2563
Free AU's: 2323
AU's read for dump: 34
Block images saved: 6661
Map lines written: 34
Heartbeats seen: 0
Corrupt metadata blocks: 0
Corrupt AT blocks: 0
...

* .map, Map files are ASCII files that describe the data in the image files for a particular disk group

$ more DATA.map
N0001 D0000 R00 A00000000 F00000000 I0 E00000000 U00 C00256 S0000 B0000000000
N0001 D0000 R00 A00000001 F00000000 I0 E00000000 U00 C00256 S0000 B0000000000
N0001 D0000 R00 A00000002 F00000001 I0 E00000000 U00 C00256 S0000 B0000000000
N0001 D0000 R00 A00000003 F00000003 I0 E00000001 U00 C00256 S0000 B0000000000
N0001 D0000 R00 A00000004 F00000003 I0 E00000011 U00 C00256 S0000 B0000000000
...
N0001 D0000 R00 A00000234 F00000267 I1 E00000000 U00 C00001 S0000 B0000000000

*.img - For each diskgroup, could be many image files. The size is limited to 2gb and will be a exact dump of the content of the diskgroup.

When you use, the extract for the disk a .img copy will be created of multiple sizes of 2gb.

amdu -diskstring="ORCL:*" -extract DATA.267 -output NSA_TN_DATA.267 -noreport -nodir

You can use this .img file with Oracle Unloader to extract the data

So with the AMDU , you can very well know your disk group structures with out having them mounted, but its just that some internals you have to know, I Urge you do not try this on production systems without knowing what exactly this utility does.

-Thanks
Geek DBA