I am trying to understand "nbmand" option of mount(1M). From the manual
page, it enables "non-blocking mandatory lock semantic" on the mounted
file system. I know the default advisory locking on Solaris and know
mandatory locking can be enabled on per file basis(by setting groud-id bit
and unsetting goup-execute bit). So I thought nbmand option is a way to
do that on file system basis, but it turned out not to be that. 

I did the following:

1) mount a UFS file system with "-o nbmand"
2) run a little program written by me to lock a file, say testfile. The program
calls fcntl(2) with F_SETLK cmd argument.
3) run "cat > testfile"

I had thought step 3 would fail with error message like "testfile: Resource
temporarily unavailable". However, it didn't. 

Can anyone tell me what is the semantic of the "non-blocking mandatory
locking", and how is it different from the traditional mandatory locking on 
System V Unix? 

Thanks,
Ray
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