Friday, June 26, 2009

ASM Disk Controller numbers can get changed if the SAN Switch is replaced


We have setup our Oracle E-Business Suite database to be highly available by using Oracle 10g RAC technology using the ASM feature. We use EMC Symmetrix for storage and a Brocade device for the SAN switch. Our SAN fabric was recently upgraded and among many changes, the legacy Brocade SAN switches were replaced by Cisco switches.


Due to this change, we rebooted both the Oracle RAC database nodes. But the database would not start because the ASM diskgroup could not be mounted. We have hardcoded the asm_diskstring parameter to a specific set of disk controller numbers. While mounting a diskgroup, the ASM instance will discover only those devices that match the asm_diskgroup parameter. Upon further investigation, we found out that the disk controller numbers got changed after the new switch installation.

Note the changed disk controller numbers in the below image


We use EMC Symmetrix as our SAN storage solution. During the initial ASM conversion project, we managed to save the syminq numbers of all our ASM devices. Because the syminq numbers do NOT change even upon a switch replacement, we could use the same syminq numbers to find out the new disk controller numbers. We then updated the asm_diskgroup initialization parameter with these new controller numbers and then the ASM diskgroup was successfully mounted and the database started.

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