vssadmin can not delete shadow

[Peter]

I tried to delete my shadow with vssadmin delete all.
Somehow the command did not work. According to vssadmin
usage information. vssadmin can only delete shadow
type:clientaccessible. But my shadow types are all
ApplicationRollback.

Can anyone tell me why my shadow type is
ApplicationRollback? How can I create shadow with
ClientAccessible type?

Thanks