Re: Oracle 10g hangs intermittently waiting for I/O

  • From: Paweł Kotlarz <pkotla@xxxxxx>
  • To: Matthew Zito <mzito@xxxxxxxxxxx>
  • Date: Fri, 15 May 2009 16:42:36 +0200

Hi Matt,
dmesg shows only timeouts on a cdrom drive and reservation conflicts on tape devices. Multipathing is not used. 

scsi3 (0,2,0) : reservation conflict
scsi3 (0,2,0) : reservation conflict
ide-cd: cmd 0x1e timed out
hda: irq timeout: status=0xd0 { Busy }
hda: irq timeout: error=0x00
hda: ATAPI reset complete
ide-cd: cmd 0x25 timed out
hda: irq timeout: status=0xd0 { Busy }
hda: irq timeout: error=0x00
hda: ATAPI reset complete


Thanks,

Pawel

On 2009-05-15 15:57, Matthew Zito wrote:

If you run a "dmesg" - do you see any errors in the kernel logs?  If the 
devices stop responding to I/O for periods of time there should be SCSI timeouts in the 
logs, or at least some warnings from the multipathing driver.

Thanks,
Matt

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mzito@xxxxxxxxxxx
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-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx on behalf of Pawel Kotlarz
Sent: Fri 5/15/2009 9:48 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: Oracle 10g hangs intermittently waiting for I/O
Hello all. 

I have oracle 10.2.0.3 data warehouse database on 11.1.0.7 ASM with
asmlib. RHEL 4.7. Proliant DL585 G2 with MSA70 storage.

The problem I face is an 'I/O hiccup'. The database can work properly
for a week or two and then suddenly keep stalling for no apparent
reason. Users complain that their selects take 2x or 3x more time.
vmstat shows I/O activity (bi, bo colums) for half a minute and for
another half a minute shows no activity (bi and bo columns equal to 0)
and a number of processes waiting for I/O (procs/b column). strace on an
oracle process waiting for I/O shows it is waiting for a completion of 'read' call. The only thing that helps is rebooting the box. 

I can isolate the problem to specific disks using iostat. These disks
are the same on a day the problem occurs but they are different on
another occurrance of the problem. Storage / Linux admins do not see any
problem on their side.

I have several one-off patches recommended by Oracle support:

Bug 5452672: Hung database instance if linux kernel miss aio request
Bug 6656824: LNX-10204-TC6  SIGSEGV AT SKGFR_REAP64()+281, IN DBW0
Bug 6087207: WARNING:ORACLE PROCESS RUNNING OUT OF OS KERNEL I/O RESOURCES
Bug 6882513 - MERGE LABEL REQUEST ON TOP OF 10.2.0.3 FOR BUGS 6801535 5576584 
Bug 5576584 (4880399): ASM PARALLEL READS PERFORMANCE NOT ACCEPTABLE

I plan to upgrade to 10.2.0.4 but need first to sort out some hash join
bugs (yet unknown to Oracle) that break our large queries with ora-600
errors.

What would you recommend to do to narrow down the problem to Oracle /
ASM / asmlib / Linux / storage fault?

Do you know of any other bugs that can show such a behaviour?

Thanks.


Pawel Kotlarz
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