Re: Removing all datafiles doesn't bring down the database

sybrandb_at_yahoo.com wrote in message news:<a1d154f4.0307170536.cf847ba_at_posting.google.com>...
> jeffyee_at_hotmail.com (Jeffrey Yee) wrote in message news:<ec4cec95.0307170154.5727fd96_at_posting.google.com>...
> > Hi,
> >
> > I'm running Oracle9i 9.0.1 on HP-UX 11i. I simulate a disk crash by
> > removing all the datafiles. To my surprise, the database keeps
> > running, and I can still do queries, update, commit, and alter system
> > switch logfile.
> >
> > But I'm confuse how this can happen. A switch logfile will cause a
> > checkpoint, causing dirty buffers to be written to datafiles, which
> > are missing.
> >
> > Even better still, after I restore & recover, I can see those commit
> > that was done after deleting all the datafiles.
> >
> > Is this something new in Oracle9i? Is there anywhere I can get more
> > information on this matter. I'm interested to know the architecture
> > behind this. I would assume most of the stuff is stored in the redo
> > logs.
> >
> > Please advice. Thank you.
> >
> >
> > Best Regards,
> > Jeffrey Yee
>
> Feature of the Unix filesystem. Has nothing to do with Oracle. The
> files are still there, because they are in cache. However they are
> ready to be overwritten, and if you bounce the system, your database
> will be toast.

Minor quibble. They are not in cache, they are still real files. What has changed is the directory entry telling the filesystem where it begins. Oracle knows where the file is from when it opened the file. If you create a new file with the same name, it will be in a different place, and any program that asks for the file will get the new one.

OP: Do a bdf or df -k to see that the disk space is still being used, then do it again after shutting down Oracle. See any unix text about inodes for more details on what is happening (I still find Unix Power Tools useful).

jg

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