Re: ASM tracking datafiles
- From: Dan Norris <dannorris@xxxxxxxxxxxxx>
- To: knecht.stefan@xxxxxxxxx, Niall Litchfield <niall.litchfield@xxxxxxxxx>
- Date: Wed, 25 Feb 2009 08:30:16 -0600
> But ASM itself doesn't "care" about files as far as I've seen so far.
I don't think that's completely accurate. ASM has to care because it is the
only one that (at least initially) knows where to find the files that the
database needs. That's what V$ASM_FILE shows (in an ASM instance). I'm not
sure where/how ASM relates each of the files in that view to
databases--maybe it doesn't care about databases?
Once the extent map for a file is given to the RDBMS instance, the ASM
instance isn't in the I/O path (it's built in to the RDBMS kernel). However,
the initial request to open a file is looked up by the ASM instance and the
extent map given to the RDBMS instance so that the RDBMS can open the file.
So, I think Niall is right that ASM doesn't necessarily know which datafiles
belong to which RDBMS, but when a request for a specific file is made from
RDBMS to ASM, it is up to ASM to locate the file and all its parts and tell
the RDBMS where to go to open the file it requested.
The information shown in V$ASM_FILE has to be stored in the ASM metadata on
the ASM disks in the diskgroup where the file resides.
Dan
Other related posts:
