In the SMF manual above the Data Set I/O Statistics Section for the Subtype 6, it does say
"Note: I/O response and service time components are recorded in multiples of 128 micro-seconds." So XDBDO0 has an average response time of 22.875ms of which 5ms is connect time and 17ms disconnect time. The high connect time would indicate the reading (or possibly the writing) of multiple pages at a time (index or table space scan). The disconnect time of 17ms could also be considered high. Disconnect time is normally from random reads or if you are synchronously mirroring these devices via PPRC it can be from writes. So there is not a "correct" average response time, as it depends on the type of I/O being executed and your environment. Typically the connect time for a single 4KB data page either read or write should be under 1ms for a modern control unit with a 2Gb FICON channel. A non-mirrored write will generally be a cache hit and therefor will not have any disconnect time. A mirrored write will have some disconnect time based on the size of the block, the speed of the link and the distance between the primary and secondary. A random read will have some disconnect time as the control unit pulls the page from the disk, and that time would depend on how busy the control unit / raid-rank was at the time. Thanks -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Ducky Duc Sent: Thursday, April 18, 2013 9:54 AM To: [email protected] Subject: SMF42 subtype 6 interpretation Hi all , As a DB2 specialist , i have reports showing a wait for io time in some programs. I did a SMF42 subtype 6 reports and , effectively, my datasets are in the top of the list , cut and pasted below from an Excel sheet. However , don't know if my calculation of the average response time of 9 ; which corresponds to 9 X 128ms = 1152ms , from the manual is correct. And sorry for the dummy question , what is a "correct" average response time , a few ms i suppose ... Thank you Duc DATASET VOLSER RESPTIME IOCOUNT AVGCONCT AVGPEND AVGDISC DB2XXF0.DSNDBD.F4DB002.F4SS102.I0001.A001 XDBDO0 22.875 5379 5.187 0.125 17.250 DB2XXF0.DSNDBD.F3DB001.F3SS039.I0001.A001 XDBDM5 21.625 1141 16.750 0.125 4.437 DB2XXF0.DSNDBD.F3DB002.F3SS113.I0001.A001 XDBD8A 14.062 7489 1.875 0.125 11.625 DB2XXF0.DSNDBD.F3DB002.IF3TADR1.I0001.A001 XDBI16 12.875 2057 1.750 0.125 10.750 DB2XXF0.DSNDBD.F3DB001.F3SS037.I0001.A001 XDBDH3 9.562 3946 6.125 0.000 3.187 DB2XXF0.DSNDBD.F3DB001.IF3T1BGJ.I0001.A001 XDBI08 9.562 2038 5.625 0.000 3.562 DB2XXF0.DSNDBD.F3DB006.F3PS006.I0001.A003 XDBD53 9.187 1244 5.875 0.125 2.937 DB2XXF0.DSNDBD.F3DB006.F3PS006.I0001.A007 XDBDC0 9.062 1203 5.750 0.125 2.937 DB2XXF0.DSNDBD.F3DB006.F3PS006.I0001.A008 XDBDF6 9.062 1321 6.000 0.125 2.687 DB2XXF0.DSNDBD.F3DB006.F3PS006.I0001.A009 XDBDKD 9.062 1321 5.750 0.125 3.062 DB2XXF0.DSNDBD.F3DB006.F3PS006.I0001.A010 XDBDI2 9.062 1328 6.250 0.125 2.375 DB2XXF0.DSNDBD.F3DB001.IF3TCCTD.I0001.A001 XDBI4C 9.062 1057 5.625 0.000 3.187 DB2XXF0.DSNDBD.F5DB001.F5SS012.I0001.A001 XDBDG0 9.062 1926 7.000 0.125 1.625 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN NOTICE: Confidential message which may be privileged. Unauthorized use/disclosure prohibited. If received in error, please go to www.td.com/legal for instructions. AVIS : Message confidentiel dont le contenu peut être privilégié. Utilisation/divulgation interdites sans permission. Si reçu par erreur, prière d'aller au www.td.com/francais/avis_juridique pour des instructions. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
