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тАО06-16-2010 09:30 AM
тАО06-16-2010 09:30 AM
Have a 11.31-box, with somes Oracle Database. The DBA wants direct IO. Mounted the database-disk with mincache and convosync:
/oracle/ORADB1/databases on /dev/vg21/lvol2 ioerror=mwdisable,largefiles,mincache=direct,delaylog,nodatainlog,convosync=direct,dev=80210002
So far so good, however, this is what tusc tells me about direct IO:
[17520] open("/oracle/ORADB2/databases/XTL/oradata/test01.dbf", O_RDONLY|0x800, 01210) ................................................. = 17
[17520] open("/oracle/ORADB2/databases/XTL/oradata/test01.dbf", O_RDONLY|0x800, 07645) ................................................. = 17
[17520] open("/oracle/ORADB2/databases/XTL/oradata/test01.dbf", O_RDWR|0x800|O_DSYNC, 030) ............................................. = 17
[17520] open("/oracle/ORADB2/databases/XTL/oradata/test01.dbf", O_RDONLY|0x800, 01210) ................................................. = 17
[17520] open("/oracle/ORADB2/databases/XTL/oradata/test01.dbf", O_RDONLY|0x800, 07645) ................................................. = 17
[17520] open("/oracle/ORADB2/databases/XTL/oradata/test01.dbf", O_RDWR|0x800|O_DSYNC, 030) ............................................. = 17
...indicating that Direct IO is NOT used. And the DBA tells me that to.
How come? What to do?
Thanks in advance.
Greetings
Danny
Solved! Go to Solution.
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тАО06-16-2010 10:48 AM
тАО06-16-2010 10:48 AM
Re: Direct io (mincache and convosync) not working?
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тАО06-16-2010 11:05 AM
тАО06-16-2010 11:05 AM
Re: Direct io (mincache and convosync) not working?
Sorry...
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тАО06-16-2010 11:19 AM
тАО06-16-2010 11:19 AM
Re: Direct io (mincache and convosync) not working?
> Tim: Disregard my response.. I cannot find proof of the comment anywhere.. I must have been dreaming...
No, you're not :-) The OnlineJFS requirement for 'convosync' and 'mincache=direct' are documented in the 'mount_vxfs(1M)' manpages.
However, if I recall correctly, without OnlinejFS the mount would fail if these options were used. A 'cat /etc/mnttab' will show what mount options are in force.
Regards!
...JRF...
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тАО06-16-2010 02:43 PM
тАО06-16-2010 02:43 PM
Re: Direct io (mincache and convosync) not working?
Thanks for your answers - and its true, these mount-options only work with OnlineJFS, which is installed on the system - the line in my initial mail, showing the mount-options for the mountpoint, are in fact from the "mount"-command - showing that the convosync and mincache are already in effect.
But still - the tusc should return direct-io for the database-files, not O_RDONLY.
So - any ideas would be appreciated.
Thanks.
Danny
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тАО06-16-2010 11:19 PM
тАО06-16-2010 11:19 PM
Re: Direct io (mincache and convosync) not working?
ARe you sure you are interpreting what you see correctly here?
Cos what I see is the same file (/oracle/ORADB2/databases/XTL/oradata/test01.dbf) being opened read-only (maybe as part of the header checks oracle does at startup), followed by it being opened read-write with the O_DSYNC flag. If you look at the mount_vxfs man page you will see when you mount with mincache=direct,convosync=direct then any files opened with O_DSYNC will bypass the filesystem buffer cache and do direct IO.
HTH
Duncan
I am an HPE Employee
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тАО06-17-2010 01:22 AM
тАО06-17-2010 01:22 AM
Re: Direct io (mincache and convosync) not working?
Thanks a bunch for your reply.
Hm - you have a valid point there, no doubt. I was trusting a MetaLink-document 555601.1, which describes how to check this. This note says, that if a datafile is opened with direct IO, the open-statements from tusc should include O_DIRECT.
To kind of verify this, I tried to:
1 - create a database-file on a filesystem, mounted without convosync and mincache=direct. It still says O_DSYNC.
2 - Alter the database to not use direct IO - still, database-files on filesystems both with or without the aforementioned mountoptions is O_DSYNC.
I might misinterpretate something but initially this kind of shows that direct IO is not working.
Im pretty sure I'm missing something crucial here, I just don't know what.
Again, thanks a lot so far.
Greetings
Danny
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тАО06-17-2010 02:27 AM
тАО06-17-2010 02:27 AM
Re: Direct io (mincache and convosync) not working?
Read the mount_vxfs man page carefully, and also have a look at what the VX_DIRECT caching advisory does when direct IO is enabled (see the vxfsio(7) man page)
HTH
Duncan
I am an HPE Employee
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тАО06-17-2010 03:00 AM
тАО06-17-2010 03:00 AM
Re: Direct io (mincache and convosync) not working?
IF it succeeds to get the Oracle database-file opened using Direct IO, will tusc then show the O_DIRECT-flag?
Sorry for all the stupid questions.
Greetings
Danny
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тАО06-17-2010 03:00 AM
тАО06-17-2010 03:00 AM
Re: Direct io (mincache and convosync) not working?
To get O_DIRECT, the application must use that in its open. I suppose open(2) could modify the system call based on the filesystem mount types.