"standby database destination mismatch"
*Cause: Another instance had access to a standby database destination
that this instance did not. If the initialization parameter
LOG_ARCHIVE_CONFIG does not define a DG_CONFIG, this
may be due to a standby database becoming unavailable recently.
*Action: Ensure that at each instance the set of standby databases referred
to by LOG_ARCHIVE_DEST_n initialization parameters is the same
and define a DG_CONFIG at each instance to identify those databases