Re: Mystery paging
IIRC, pages read from SPOOL-resident DCSSs are counted as paging I/O, so the scenario you describe in your third paragraph is certainly a possibility. Marty -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Bill Holder Sent: Monday, May 19, 2008 3:30 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: Mystery paging The dataspace usage is certainly a good thing to check, but there are at least a couple of other possibilities: The paging rate numbers are across time, whereas the Q ALLOC PAGE output is instantaneous. It could be that there's a low volume of paging to/from paging DASD going on, but the pages that are read in are immediately changed, which would cause CP to discard the copy out on paging DASD when CP notices the page change. So it needn't be the same page read 13 times a second, it could be a bunch of different pages which are then immediately changed, for which CP then discards the paging DASD copy. I'd have to check, but it seems possible that demand paging of spool pages from (and even possibly to) spool volumes could account for this, I'd have to check how those get counted. In particular, if you have a very lightly used NSS or DCSS, that only tends to be loaded by one user at a time, and it is frequently purged and then reloaded, the initial page fault block reads from spool might show up like this. - Bill Holder z/VM development, IBM
Re: Mystery paging
The dataspace usage is certainly a good thing to check, but there are at least a couple of other possibilities: The paging rate numbers are across time, whereas the Q ALLOC PAGE output is instantaneous. It could be that there's a low volume of paging to/from p aging DASD going on, but the pages that are read in are immediately changed, wh ich would cause CP to discard the copy out on paging DASD when CP notices the page change. So it needn't be the same page read 13 times a second, it could be a bunch of different pages which are then immediately changed, for which CP then discards the paging DASD copy. I'd have to check, but it seems possible that demand paging of spool page s from (and even possibly to) spool volumes could account for this, I'd hav e to check how those get counted. In particular, if you have a very lightly u sed NSS or DCSS, that only tends to be loaded by one user at a time, and it i s frequently purged and then reloaded, the initial page fault block reads f rom spool might show up like this. - Bill Holder z/VM development, IBM
Re: Mystery paging
Kris, NOMAD servers are not listed in QUERY RESOURCES. After thinking about it some more, I seriously doubt they use dataspaces. Most of the NOMAD code predates the existence of dataspaces. Bill Holder's explanation is more likely. The workload on the system is CMS, so I'm sure there's a fair amount of segment usage. It's not a problem, just curiosity, so I won't worry too much about it. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Kris Buelens Sent: Saturday, May 17, 2008 13:57 To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] Mystery paging Maybe Q RESOURCES will reveal the userids of the NOMAD servers, then Q SPACES USER will show some dataspaces. 2008/5/17 O'Brien, Dennis L Dennis.L.O'[EMAIL PROTECTED]: Kris, Thanks. That's interesting reading. The system in question does not have DB2/VM, and the 3 SFS filepools have no directories eligible for dataspaces. Any other ideas? Do NOMAD2 Shared Databases use dataspaces? I know this system has NOMAD2 Shared Databases, but as we're just getting familiar with it, I don't know their userids. I don't think there's anything wrong with the system, it's just curiosity, so it's not worth any great effort. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Kris Buelens Sent: Saturday, May 17, 2008 11:52 To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] Mystery paging Are dataspaces being used? DB2 and SFS are the the most common examples. With dataspaces (mapped to minidisks), the application simply reference the storage, CP will page-in what is referenced, and that is counted as paging. CP's Q SPACES and IND SPACE commands can help you. On VM's web-site, there is a document were I describe this in more detail: http://www.vm.ibm.com/perf/tips/dim.html http://www.vm.ibm.com/perf/tips/vmdspage.html 2008/5/17 O'Brien, Dennis L Dennis.L.O'[EMAIL PROTECTED]: We recently inherited responsibility for a z/VM 5.2 system that had been maintained by another group. They had a DR test today, and I logged on and looked around. The LPAR is configured with 3G central storage and no expanded storage. I issued the following commands: q alloc page EXTENT EXTENT TOTAL PAGES HIGH% VOLID RDEV STARTEND PAGES IN USE PAGE USED -- -- -- -- -- -- VMPG00 8719 1 1000 18 1 1 1% VMPG01 871A 1 1000 18 0 0 0% VMPG02 871B 1 1000 18 0 0 0% VMPG03 871C 1 1000 18 0 0 0% -- -- SUMMARY 72 1 1% USABLE72 1 1% Ready; ind AVGPROC-003% 01 MDC READS-000112/SEC WRITES-03/SEC HIT RATIO-093% PAGING-13/SEC STEAL-000% Q0-3(0) DORMANT-00141 Q1-0(0) E1-0(0) Q2-1(0) EXPAN-001 E2-0(0) Q3-0(0) EXPAN-001 E3-0(0) PROC -003% LIMITED-0 Ready; q xstor Expanded storage is not available within this hardware configuration. Ready(01401); Since there's no expanded storage, where are those 13 pages/second going? Is the system reading the one page that's out on DASD 13 times a second? I did another Q ALLOC PAGE after the IND, and there's still only one page out there. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -- Kris Buelens, IBM Belgium, VM customer support -- Kris Buelens, IBM Belgium, VM customer support
Re: Mystery paging
Dennis, NOMAD Shared Databases can utilize dataspaces. It's implemented by merely adding a LOOKUP DATASPACE clause to the desired MASTER definitions, then issuing a SCHEMA CHECK command. No application code need change to take advantage of the facility. So it's conceivable a DBA implemented dataspace use at the database level, with the unmodified application code transparently benefiting from this database enhancement. Regards, Tom Ramsberger Select Business Solutions Kris, NOMAD servers are not listed in QUERY RESOURCES. After thinking about it some more, I seriously doubt they use dataspaces. Most of the NOMAD code predates the existence of dataspaces. Bill Holder's explanation is more likely. The workload on the system is CMS, so I'm sure there's a fair amount of segment usage. It's not a problem, just curiosity, so I won't worry too much about it. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Kris Buelens Sent: Saturday, May 17, 2008 13:57 To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] Mystery paging Maybe Q RESOURCES will reveal the userids of the NOMAD servers, then Q SPACES USER will show some dataspaces. 2008/5/17 O'Brien, Dennis L Dennis.L.O'[EMAIL PROTECTED]: Kris, Thanks. That's interesting reading. The system in question does not have DB2/VM, and the 3 SFS filepools have no directories eligible for dataspaces. Any other ideas? Do NOMAD2 Shared Databases use dataspaces? I know this system has NOMAD2 Shared Databases, but as we're just getting familiar with it, I don't know their userids. I don't think there's anything wrong with the system, it's just curiosity, so it's not worth any great effort. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Kris Buelens Sent: Saturday, May 17, 2008 11:52 To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] Mystery paging Are dataspaces being used? DB2 and SFS are the the most common examples. With dataspaces (mapped to minidisks), the application simply reference the storage, CP will page-in what is referenced, and that is counted as paging. CP's Q SPACES and IND SPACE commands can help you. On VM's web-site, there is a document were I describe this in more detail: http://www.vm.ibm.com/perf/tips/dim.html http://www.vm.ibm.com/perf/tips/vmdspage.html 2008/5/17 O'Brien, Dennis L Dennis.L.O'[EMAIL PROTECTED]: We recently inherited responsibility for a z/VM 5.2 system that had been maintained by another group. They had a DR test today, and I logged on and looked around. The LPAR is configured with 3G central storage and no expanded storage. I issued the following commands: q alloc page EXTENT EXTENT TOTAL PAGES HIGH% VOLID RDEV STARTEND PAGES IN USE PAGE USED -- -- -- -- -- -- VMPG00 8719 1 1000 18 1 1 1% VMPG01 871A 1 1000 18 0 0 0% VMPG02 871B 1 1000 18 0 0 0% VMPG03 871C 1 1000 18 0 0 0% -- -- SUMMARY 72 1 1% USABLE72 1 1% Ready; ind AVGPROC-003% 01 MDC READS-000112/SEC WRITES-03/SEC HIT RATIO-093% PAGING-13/SEC STEAL-000% Q0-3(0) DORMANT-00141 Q1-0(0) E1-0(0) Q2-1(0) EXPAN-001 E2-0(0) Q3-0(0) EXPAN-001 E3-0(0) PROC -003% LIMITED-0 Ready; q xstor Expanded storage is not available within this hardware configuration. Ready(01401); Since there's no expanded storage, where are those 13 pages/second going? Is the system reading the one page that's out on DASD 13 times a second? I did another Q ALLOC PAGE after the IND, and there's still only one page out there. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -- Kris Buelens, IBM Belgium, VM customer support -- Kris Buelens, IBM Belgium, VM customer support
Mystery paging
We recently inherited responsibility for a z/VM 5.2 system that had been maintained by another group. They had a DR test today, and I logged on and looked around. The LPAR is configured with 3G central storage and no expanded storage. I issued the following commands: q alloc page EXTENT EXTENT TOTAL PAGES HIGH% VOLID RDEV STARTEND PAGES IN USE PAGE USED -- -- -- -- -- -- VMPG00 8719 1 1000 18 1 1 1% VMPG01 871A 1 1000 18 0 0 0% VMPG02 871B 1 1000 18 0 0 0% VMPG03 871C 1 1000 18 0 0 0% -- -- SUMMARY 72 1 1% USABLE72 1 1% Ready; ind AVGPROC-003% 01 MDC READS-000112/SEC WRITES-03/SEC HIT RATIO-093% PAGING-13/SEC STEAL-000% Q0-3(0) DORMANT-00141 Q1-0(0) E1-0(0) Q2-1(0) EXPAN-001 E2-0(0) Q3-0(0) EXPAN-001 E3-0(0) PROC -003% LIMITED-0 Ready; q xstor Expanded storage is not available within this hardware configuration. Ready(01401); Since there's no expanded storage, where are those 13 pages/second going? Is the system reading the one page that's out on DASD 13 times a second? I did another Q ALLOC PAGE after the IND, and there's still only one page out there. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller
Re: Mystery paging
Are dataspaces being used? DB2 and SFS are the the most common examples. With dataspaces (mapped to minidisks), the application simply reference the storage, CP will page-in what is referenced, and that is counted as paging. CP's Q SPACES and IND SPACE commands can help you. On VM's web-site, there is a document were I describe this in more detail: http://www.vm.ibm.com/perf/tips/dim.html http://www.vm.ibm.com/perf/tips/vmdspage.html 2008/5/17 O'Brien, Dennis L Dennis.L.O'[EMAIL PROTECTED]: We recently inherited responsibility for a z/VM 5.2 system that had been maintained by another group. They had a DR test today, and I logged on and looked around. The LPAR is configured with 3G central storage and no expanded storage. I issued the following commands: q alloc page EXTENT EXTENT TOTAL PAGES HIGH% VOLID RDEV STARTEND PAGES IN USE PAGE USED -- -- -- -- -- -- VMPG00 8719 1 1000 18 1 1 1% VMPG01 871A 1 1000 18 0 0 0% VMPG02 871B 1 1000 18 0 0 0% VMPG03 871C 1 1000 18 0 0 0% -- -- SUMMARY 72 1 1% USABLE72 1 1% Ready; ind AVGPROC-003% 01 MDC READS-000112/SEC WRITES-03/SEC HIT RATIO-093% PAGING-13/SEC STEAL-000% Q0-3(0) DORMANT-00141 Q1-0(0) E1-0(0) Q2-1(0) EXPAN-001 E2-0(0) Q3-0(0) EXPAN-001 E3-0(0) PROC -003% LIMITED-0 Ready; q xstor Expanded storage is not available within this hardware configuration. Ready(01401); Since there's no expanded storage, where are those 13 pages/second going? Is the system reading the one page that's out on DASD 13 times a second? I did another Q ALLOC PAGE after the IND, and there's still only one page out there. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -- Kris Buelens, IBM Belgium, VM customer support
Re: Mystery paging
Kris, Thanks. That's interesting reading. The system in question does not have DB2/VM, and the 3 SFS filepools have no directories eligible for dataspaces. Any other ideas? Do NOMAD2 Shared Databases use dataspaces? I know this system has NOMAD2 Shared Databases, but as we're just getting familiar with it, I don't know their userids. I don't think there's anything wrong with the system, it's just curiosity, so it's not worth any great effort. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Kris Buelens Sent: Saturday, May 17, 2008 11:52 To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] Mystery paging Are dataspaces being used? DB2 and SFS are the the most common examples. With dataspaces (mapped to minidisks), the application simply reference the storage, CP will page-in what is referenced, and that is counted as paging. CP's Q SPACES and IND SPACE commands can help you. On VM's web-site, there is a document were I describe this in more detail: http://www.vm.ibm.com/perf/tips/dim.html http://www.vm.ibm.com/perf/tips/vmdspage.html 2008/5/17 O'Brien, Dennis L Dennis.L.O'[EMAIL PROTECTED]: We recently inherited responsibility for a z/VM 5.2 system that had been maintained by another group. They had a DR test today, and I logged on and looked around. The LPAR is configured with 3G central storage and no expanded storage. I issued the following commands: q alloc page EXTENT EXTENT TOTAL PAGES HIGH% VOLID RDEV STARTEND PAGES IN USE PAGE USED -- -- -- -- -- -- VMPG00 8719 1 1000 18 1 1 1% VMPG01 871A 1 1000 18 0 0 0% VMPG02 871B 1 1000 18 0 0 0% VMPG03 871C 1 1000 18 0 0 0% -- -- SUMMARY 72 1 1% USABLE72 1 1% Ready; ind AVGPROC-003% 01 MDC READS-000112/SEC WRITES-03/SEC HIT RATIO-093% PAGING-13/SEC STEAL-000% Q0-3(0) DORMANT-00141 Q1-0(0) E1-0(0) Q2-1(0) EXPAN-001 E2-0(0) Q3-0(0) EXPAN-001 E3-0(0) PROC -003% LIMITED-0 Ready; q xstor Expanded storage is not available within this hardware configuration. Ready(01401); Since there's no expanded storage, where are those 13 pages/second going? Is the system reading the one page that's out on DASD 13 times a second? I did another Q ALLOC PAGE after the IND, and there's still only one page out there. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -- Kris Buelens, IBM Belgium, VM customer support
Re: Mystery paging
Maybe Q RESOURCES will reveal the userids of the NOMAD servers, then Q SPACES USER will show some dataspaces. 2008/5/17 O'Brien, Dennis L Dennis.L.O'[EMAIL PROTECTED]: Kris, Thanks. That's interesting reading. The system in question does not have DB2/VM, and the 3 SFS filepools have no directories eligible for dataspaces. Any other ideas? Do NOMAD2 Shared Databases use dataspaces? I know this system has NOMAD2 Shared Databases, but as we're just getting familiar with it, I don't know their userids. I don't think there's anything wrong with the system, it's just curiosity, so it's not worth any great effort. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -Original Message- From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On Behalf Of Kris Buelens Sent: Saturday, May 17, 2008 11:52 To: IBMVM@LISTSERV.UARK.EDU Subject: Re: [IBMVM] Mystery paging Are dataspaces being used? DB2 and SFS are the the most common examples. With dataspaces (mapped to minidisks), the application simply reference the storage, CP will page-in what is referenced, and that is counted as paging. CP's Q SPACES and IND SPACE commands can help you. On VM's web-site, there is a document were I describe this in more detail: http://www.vm.ibm.com/perf/tips/dim.html http://www.vm.ibm.com/perf/tips/vmdspage.html 2008/5/17 O'Brien, Dennis L Dennis.L.O'[EMAIL PROTECTED]: We recently inherited responsibility for a z/VM 5.2 system that had been maintained by another group. They had a DR test today, and I logged on and looked around. The LPAR is configured with 3G central storage and no expanded storage. I issued the following commands: q alloc page EXTENT EXTENT TOTAL PAGES HIGH% VOLID RDEV STARTEND PAGES IN USE PAGE USED -- -- -- -- -- -- VMPG00 8719 1 1000 18 1 1 1% VMPG01 871A 1 1000 18 0 0 0% VMPG02 871B 1 1000 18 0 0 0% VMPG03 871C 1 1000 18 0 0 0% -- -- SUMMARY 72 1 1% USABLE72 1 1% Ready; ind AVGPROC-003% 01 MDC READS-000112/SEC WRITES-03/SEC HIT RATIO-093% PAGING-13/SEC STEAL-000% Q0-3(0) DORMANT-00141 Q1-0(0) E1-0(0) Q2-1(0) EXPAN-001 E2-0(0) Q3-0(0) EXPAN-001 E3-0(0) PROC -003% LIMITED-0 Ready; q xstor Expanded storage is not available within this hardware configuration. Ready(01401); Since there's no expanded storage, where are those 13 pages/second going? Is the system reading the one page that's out on DASD 13 times a second? I did another Q ALLOC PAGE after the IND, and there's still only one page out there. Dennis O'Brien Elected office holds more perks than Elvis' nightstand. -- Dennis Miller -- Kris Buelens, IBM Belgium, VM customer support -- Kris Buelens, IBM Belgium, VM customer support
