Data … as usual

In a previous post, I explained how to dump ASM Disk header and how to analyze it. This method, which used kfed binary, is a little bit complex because of fields with a complex name extracted from the internal structure.

Another way to proceed and to see main information about asm disks is to use an undocumented binary located in $ORACLE_HOME/bin named amdu.

If amdu is not available in your $ORACLE_HOME/bin directory, you can build it with the next make command:

[oracle@oel ~]$ make -f $ORACLE_HOME/rdbms/lib/ins_rdbms.mk iamdu

To dump your ASM diskheader, you just have to execute this command with the -diskstring option and specify the location of your ASM disk devices (default uses ASM lib directory):

[oracle@oel ~]$ amdu -diskstring='/dev/oracleasm/disks/*'
amdu_2012_03_21_11_14_36/

Now, change directory to the output generated and have a look to the report.txt file:

[oracle@oel ~]$ cd amdu_2012_03_21_11_14_36/
[oracle@oel amdu_2012_03_21_11_14_36]$ cat report.txt
-*-amdu-*-
******************************* AMDU Settings ********************************
ORACLE_HOME = /u01/app/oracle/product/11.2.0.3/dbhome_1
System name: Linux
Node name: oel
Release: 2.6.18-274.18.1.0.1.el5
Version: #1 SMP Thu Feb 9 19:07:16 EST 2012
Machine: x86_64
amdu run: 21-MAR-12 11:14:36
Endianess: 1
--------------------------------- Operations ---------------------------------
------------------------------- Disk Selection -------------------------------
 -diskstring '/dev/oracleasm/disks/*'
------------------------------ Reading Control -------------------------------
------------------------------- Output Control -------------------------------
********************************* DISCOVERY **********************************
----------------------------- DISK REPORT N0001 ------------------------------
 Disk Path: /dev/oracleasm/disks/ASM1
 Unique Disk ID:
 Disk Label:
 Physical Sector Size: 512 bytes
 Disk Size: 1019 megabytes
 Group Name: DATA
 Disk Name: DATA_0000
 Failure Group Name: DATA_0000
 Disk Number: 0
 Header Status: 3
 Disk Creation Time: 2011/05/27 10:57:54.822000
 Last Mount Time: 2012/03/21 08:54:10.221000
 Compatibility Version: 0x0b200000(11020000)
 Disk Sector Size: 512 bytes
 Disk size in AUs: 1019 AUs
 Group Redundancy: 1
 Metadata Block Size: 4096 bytes
 AU Size: 1048576 bytes
 Stride: 113792 AUs
 Group Creation Time: 2011/05/27 10:57:54.456000
 File 1 Block 1 location: AU 2
 OCR Present: NO
----------------------------- DISK REPORT N0002 ------------------------------
 Disk Path: /dev/oracleasm/disks/ASM2
 Unique Disk ID:
 Disk Label:
 Physical Sector Size: 512 bytes
 Disk Size: 1019 megabytes
 Group Name: DATA
 Disk Name: DATA_0001
 Failure Group Name: DATA_0001
 Disk Number: 1
 Header Status: 3
 Disk Creation Time: 2011/05/27 10:57:54.822000
 Last Mount Time: 2012/03/21 08:54:10.221000
 Compatibility Version: 0x0b200000(11020000)
 Disk Sector Size: 512 bytes
 Disk size in AUs: 1019 AUs
 Group Redundancy: 1
 Metadata Block Size: 4096 bytes
 AU Size: 1048576 bytes
 Stride: 113792 AUs
 Group Creation Time: 2011/05/27 10:57:54.456000
 File 1 Block 1 location: AU 0
 OCR Present: NO
******************************* END OF REPORT ********************************

As mentioned, now you know if your disk is part of a disk group, the DG Allocation Unit size, disk size, last mounted time etc.

Of course, this tool can be used regarless of the asm instance status.