MVS guarantees that a dataonly volume being unavailable does not cause a metadataok volume to be 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.
Some VxFS operations that do not access the missing dataonly volume and function normally include the following:
Mounting the multi-volume file system, regardless if the file system is read-only or read/write.
Performing a fsck replay. Logged writes are converted to normal writes if the corresponding volume is dataonly.
Performing a full fsck.
Using all other commands that do not access data on a missing volume.
Some operations that could fail if a dataonly volume is missing include:
Reading or writing file data if the file's data extents were allocated from the missing dataonly volume.
Using the vxdump command.
Volume availability is supported only on a file system with disk layout Version 7 or later.