It was quite interesting situation when one customer contacted me and asked for the maximum length of ASM_DISKGROUP parameter’s value.

I remembered that the maximum number of diskgroups is 63 but stuck with asked question…

So I think this information may be useful to others.


  • if You have a lot of diskgroups and You’re at ASM version 10.2 then You have one more reason to upgrade your ASM instance to version 11.x


  • ASM_DISKGROUPS parameter only limits the set of diskgroups that will be automatically mounted on instance startup, so You may have diskgrpous not mentioned with this parameter, but You will need to mount them manually.
  • different instances of RAC may have different values for this parameter, so You may specify just a subset of diskgroups which are used on specific node

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