MVS guarantees the availability of some volumes even when others are unavailable. This allows you to mount a multi-volume file system even if one or more component dataonly volumes are missing.
The volumes are separated by whether metadata is allowed on the volume. An
I/O error on a dataonly volume does not affect access to any other volumes. All VxFS operations that do not access the missing dataonly volume function normally, including:
fsckreplay. Logged writes are converted to normal writes if the corresponding volume is dataonly.
Some operations that could fail if a dataonly volume is missing include:
Volume availability is supported only on a file system with disk layout Version 7 or later.
Do not mount a multi-volume system with the
wdisable mount options if the volumes have different availability properties. Symantec recommends the
mdisable mount option for cluster mounts and
ioerror=mwdisable for local mounts.