Switching VGs from concurrent mode without varyoff?

I recently got an Email asking:

In HACMP, is it possible to pass a vg varied on in enhanced mode to varied on in non-enhanced mode without any varyoff ?

As far as I know, it’s not. There are some operations that cannot be performed on a VG varied on in concurrent mode, usually anything modifying the VG structure.

If we need to do something that will modify the structure of the volume groups, we do it during a regularly scheduled downtime. This ensures that the applications aren’t writing to the VG, and we can safely make modifications. You don’t even necessarily have to bring down the HACMP resource groups. Simply unmount all the filesystems, or stop all the applications that may have any raw LVs open, varyoff the VG on all the nodes, then do a varyonvg on just one node. After you’ve made your changes it’s again simple to varyoff the VG, and run the appropritate commands to vary it back on in concurrent mode on the appropriate nodes. Just be sure that the VGs are in active or passive mode appropriately before you bring the applications back up.

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