how to low-level format a hard disk using AIX?

I have a server with AIX 6.1 , I formated some hdisks using diag tool, but in some way some of its VGDA survived.

how may I lo开发者_JAVA技巧w-level format a hard disk using AIX?

or

how may I clear the VGDA of a specific hdisk?

thanks

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dd if=/dev/zero of= with an optional bs= count= will clear off anything to zero.