- ORA-15029: disk "string"
is already mounted by this instance
attempt was made to add to a diskgroup a disk that was
already mounted by the current instance as part of some
(possibly other) diskgroup.
a different disk in the command. Note that not even the
FORCE option can be used to correct the situation until the
diskgroup containing the disk becomes dismounted by this
Bug #3265676 MAY create problems with this:
rebalancing of a diskgroup activated by a drop disk command
finished, an add disk command will stop the original rebalance
pre-maturely even though the 2nd command failed with an expected