CMMVC6571E: The command has failed because the I/O group that manages the volume that you specified was offline when you submitted the command. You can use the -force flag to force the operation, which might result in the loss of cache data.

Note: Use of the -force flag when you change the cache mode might result in loss of the cache data for the volume, depending on the current cache mode and requested cache mode. One example of a risk of potential loss of cache data would be changing the cache mode from readwrite to none.