onstat -g ath

Can someone point me to a doc explaining what the status of IO Wait means with the above onstat command. I have attempted to explain it to my Unix admins, but they just don't get it...and claim the San never is busy... Thanks in advance ... Peter Logan Senior Database Administrator Phone: 616/878-8309

Peter, Unless your entire database is in memory, then you will see an IO Wait status from time to time. That simply means that the thread is trying to read something which is currently not in the the buffer pool. The IO devices don't have to appear to be overused. From: "Peter_Logan@spartanstores.com" <Peter_Logan@spartanstores.com> To: ids@iiug.org Date: 12/08/2011 07:25 AM Subject: onstat -g ath [25574] Sent by: ids-bounces@iiug.org Can someone point me to a doc explaining what the status of IO Wait means with the above onstat command. I have attempted to explain it to my Unix admins, but they just don't get it...and claim the San never is busy... Thanks in advance ... Peter Logan Senior Database Administrator Phone: 616/878-8309 ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.

Ok, but would it be normal to always see 2 or 3 threads in this state? System is pretty busy... Peter Logan Senior Database Administrator Phone: 616/878-8309 From: "Madison Pruet" <mpruet@us.ibm.com> To: ids@iiug.org Date: 12/08/2011 09:49 AM Subject: Re: onstat -g ath [25575] Sent by: ids-bounces@iiug.org Peter, Unless your entire database is in memory, then you will see an IO Wait status from time to time. That simply means that the thread is trying to read something which is currently not in the the buffer pool. The IO devices don't have to appear to be overused. From: "Peter_Logan@spartanstores.com" <Peter_Logan@spartanstores.com> To: ids@iiug.org Date: 12/08/2011 07:25 AM Subject: onstat -g ath [25574] Sent by: ids-bounces@iiug.org Can someone point me to a doc explaining what the status of IO Wait means with the above onstat command. I have attempted to explain it to my Unix admins, but they just don't get it...and claim the San never is busy... Thanks in advance ... Peter Logan Senior Database Administrator Phone: 616/878-8309 ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum. ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.

If they are the same threads, then I would suspect that they are doing sequential scans. Also you might want to check onstat -p and see if you need to increase the size of the buffer pool. From: "Peter_Logan@spartanstores.com" <Peter_Logan@spartanstores.com> To: ids@iiug.org Date: 12/08/2011 09:02 AM Subject: Re: onstat -g ath [25576] Sent by: ids-bounces@iiug.org Ok, but would it be normal to always see 2 or 3 threads in this state? System is pretty busy... Peter Logan Senior Database Administrator Phone: 616/878-8309 From: "Madison Pruet" <mpruet@us.ibm.com> To: ids@iiug.org Date: 12/08/2011 09:49 AM Subject: Re: onstat -g ath [25575] Sent by: ids-bounces@iiug.org Peter, Unless your entire database is in memory, then you will see an IO Wait status from time to time. That simply means that the thread is trying to read something which is currently not in the the buffer pool. The IO devices don't have to appear to be overused. From: "Peter_Logan@spartanstores.com" <Peter_Logan@spartanstores.com> To: ids@iiug.org Date: 12/08/2011 07:25 AM Subject: onstat -g ath [25574] Sent by: ids-bounces@iiug.org Can someone point me to a doc explaining what the status of IO Wait means with the above onstat command. I have attempted to explain it to my Unix admins, but they just don't get it...and claim the San never is busy... Thanks in advance ... Peter Logan Senior Database Administrator Phone: 616/878-8309 ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum. ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum. ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.

My understanding is that these IO Waits are just a user thread waiting for the aio VP or kaio thread to retrieve data. Not normally a concern thing unless it is pervasive. Art Art S. Kagel Advanced DataTools (www.advancedatatools.com) Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on my employer, Advanced DataTools, the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Thu, Dec 8, 2011 at 8:25 AM, Peter_Logan@spartanstores.com < Peter_Logan@spartanstores.com> wrote: > Can someone point me to a doc explaining what the status of IO Wait means > with the above onstat command. I have attempted to explain it to my Unix > admins, but they just don't get it...and claim the San never is busy... > > Thanks in advance ... > > Peter Logan > Senior Database Administrator > Phone: 616/878-8309 > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --e89a8f234b6131223004b3966d4d

if ! kaio && ! auto aiovp then check to see if you have enough aiovps configured. onstat -g iov , the last few should not be relatively busy (< 1.0 i/o per sec.) usual suspects : check for hot spots on disk (onstat -g iof; onstat -D). check for seq scans (onstat -g tpf | awk '{print $1 " " $18}' use oat->sql explorer to drill down on queries that have highest i/o wait time . If you don't have oat it sets up quickly. http://www.openadmintool.org/