Ethan, AIX performs all file i/o via the OS's virtual memory. In other words, the VM (which is a combination of both the RAM and the Swap) is used for both executable (OS/user code) and user's memory area as well as for I/O buffers. This allocation is dynamic and certain upper and lower limits are set by the parameters in vmtune. At times of high i/o, you will find that the 'fre' mem (seen in vmstat' goes down drastically and the po/fr/sr goes up drastically as a result of old memory pages that served file i/o buffers are paged out. This is normal and in line with what you are observing and is similar to Solaris.
What you *should* be concerned about is excessive values in 'pi' as this indicates excessive paging-*in*, probably due to earlier pageouts of live pages that are still required. You are probably seeing high I/o waits since there is a lot of writes (paging out) to the swap area. 'iostat' will probably indicate that disks that host your swap area are almost 100% loaded. In this case, you should make sure that you (a) spread out swap on multiple disks, making sure that they are NOT on RAID-5. (b) allocate dedicated drives to swap areas if possible (no RAID5!). FWIW, vmstat in Solaris is able to distinguish between pi/po values for executable, file i/o and 'other' (?) types of paging. Can you find out for us if AIX also provides this? (Don't have access to an AIX box). Merry Christmas and a Blessed New Year! John Kanagaraj Oracle Applications DBA DBSoft Inc (W): 408-970-7002 Wanna know the reason for the season? Click on 'http://www.needhim.org' ** The opinions and statements above are entirely my own and not those of my employer or clients ** > -----Original Message----- > From: Post, Ethan [mailto:[EMAIL PROTECTED]] > Sent: Thursday, December 20, 2001 10:35 AM > To: Multiple recipients of list ORACLE-L > Subject: Excessive Paging - AIX Related? > > > Sorry for the cross post if you are the other big list. > > I am having some trouble finding a solution to a problem. This is > specifically AIX related. Here is the gist. > > * Any large sort or import appears to cause paging to take > place. I only > say large because of the problems, in reality these are quite > small objects > for the machine we are running, 200,000 - 600,000 rows in the > 200-400 MB > range. Any way last night I was importing one of these objects. > > * CPU wio goes through the roof almost right away. Spending > up to 50% of > time waiting on IO. > > * vmstat shows huge numbers in po, fr, sr and a few block > processes in b > column. > > * hdisk0 goes 100% (swap space is here) > > * lsps -a shows swap space is only 40% utilized, never > changes. There is > only 2GB of swap, admin just increase to 4 GB but still on > same disk. Not > sure this will really help since it never was 100% anyway. > > * Setup- RS/6000 7026-M80 rack mount running AIX with > 4-500Mhz processors, > 4GB memory, 3-10/100 Ethernet cards, 2 fiber ports, and > 2-18.2GB internal > drives with RAID. The 2 fiber ports will attach to a storage > area network > providing access to EMC Clarion storage (see below) > > * Oracle is the only app on the box and I have configured > about 2GB for the > SGA. There should be plenty of free memory. > > I am pretty sure we hosed something up with are memory > configuration. I see > a lot of things about using vmtune to configure various AIC related > parameters as too how much memory is can use for various > things. Can anyone > provide me with the direction to head in examining our > configuration and > what settings should/could be changed to improve the situation? > > Thanks, > Ethan Post > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.com > -- > Author: Post, Ethan > INET: [EMAIL PROTECTED] > > Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 > San Diego, California -- Public Internet access / Mailing Lists > -------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: John Kanagaraj INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
