Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
Specifically, see http://www.bitsavers.org/pdf/ibm/dasd/reference_summary/GX26-4577-0_3390_Reference_Summary_Jun89.pdf, This reference Summary booklet contains on p10 the non-trivial calculation formula for how many physical blocks will fit in a 3390 track, and also contains a chart on p18 showing the number of physical blocks per track for all possible block sizes based on that formula. A 3390 CKD device requires allocation for Count and Key fields in addition to the actual Data block, and space for gaps between fields and blocks. Even though all 3390 devices these days are emulated on other physical devices, the Operating System still thinks it is dealing with a 3390 device. The useful space on each track must be calculated by the rules of 3390 architecture in order that all applications and access methods sensitive to the DASD architecture will continue to work correctly. Joel C. Ewing On 10/25/21 09:44, Oscar wrote: Hi there, There's something I'm being missing, but acording to my numbers, there should be 13, not 12: Bytes per track: 56,664 bytes Bytes accessible per track: 55,996 bytes CI size: 4096 Physical record size: 4096 bytes Physical records per track (Bytes accessible per track / physical record size): 55,996 / 4096 = 13.6708984375 = 13 What I'm missing? Thanks! -- Oscar -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- Joel C. Ewing -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
And also remember that if the data sets are extended format then each physical block is 32 bytes larger. Lennie Dymoke-Bradshaw https://rsclweb.com ‘Dance like no one is watching. Encrypt like everyone is.’ -Original Message- From: IBM Mainframe Discussion List On Behalf Of Radoslaw Skorupka Sent: 25 October 2021 16:40 To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13? W dniu 25.10.2021 o 16:44, Oscar pisze: > Hi there, > > There's something I'm being missing, but acording to my numbers, there > should be 13, not 12: > > Bytes per track: 56,664 bytes > Bytes accessible per track: 55,996 bytes CI size: 4096 Physical record > size: 4096 bytes > > Physical records per track (Bytes accessible per track / physical > record size): 55,996 / 4096 = 13.6708984375 = 13 > > What I'm missing? You're missing CKD deep details. Instead of looking for old documentation just do some quick test: allocate single-track datasets. Each of them can be VSAM or just PS, it doesn't matter. However for PS it would be a little bit easier. Important: specify RECFM=F and LRECL=BLKSIZE=n, where n is any number you want to test. I would suggest the following: n=10 n=512 n=4096 Then use your ISPF editor to fill the datasets with some data. You will find out how many records/blocks fit on a track. Note: you won't get more than 86 blocks per track. Even very short ones. Reason? Gaps between blocks. More specifically: you block (physical records) consist of C and D. CKD is for Count Key Data. Your PS file has no K, so it is just C D. And gaps between them. And R0 which is also some physical record. And HA - Home Address, another 5-byte physical record. And 3390 is FBA under cover, with cell size=34B. And all the gaps or physical records (including C as separate entity) occupy one or more cells, not fraction. BTW: The above is part of "extra material" which I sometimes teach during VSAM course. -- Radoslaw Skorupka Lodz, Poland -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
There used to be a command on the CBT tape to do track capacity calculations. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of Radoslaw Skorupka [r.skoru...@hotmail.com] Sent: Monday, October 25, 2021 11:39 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13? W dniu 25.10.2021 o 16:44, Oscar pisze: > Hi there, > > There's something I'm being missing, but acording to my numbers, there > should be 13, not 12: > > Bytes per track: 56,664 bytes > Bytes accessible per track: 55,996 bytes > CI size: 4096 > Physical record size: 4096 bytes > > Physical records per track (Bytes accessible per track / physical > record size): 55,996 / 4096 = 13.6708984375 = 13 > > What I'm missing? You're missing CKD deep details. Instead of looking for old documentation just do some quick test: allocate single-track datasets. Each of them can be VSAM or just PS, it doesn't matter. However for PS it would be a little bit easier. Important: specify RECFM=F and LRECL=BLKSIZE=n, where n is any number you want to test. I would suggest the following: n=10 n=512 n=4096 Then use your ISPF editor to fill the datasets with some data. You will find out how many records/blocks fit on a track. Note: you won't get more than 86 blocks per track. Even very short ones. Reason? Gaps between blocks. More specifically: you block (physical records) consist of C and D. CKD is for Count Key Data. Your PS file has no K, so it is just C D. And gaps between them. And R0 which is also some physical record. And HA - Home Address, another 5-byte physical record. And 3390 is FBA under cover, with cell size=34B. And all the gaps or physical records (including C as separate entity) occupy one or more cells, not fraction. BTW: The above is part of "extra material" which I sometimes teach during VSAM course. -- Radoslaw Skorupka Lodz, Poland -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
There's a description of track capacity calculations in one of the DFSMS manuals; there are all sorts of overhead factors that have to be taken into account. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of Oscar [os...@naiandei.net] Sent: Monday, October 25, 2021 10:44 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13? Hi there, There's something I'm being missing, but acording to my numbers, there should be 13, not 12: Bytes per track: 56,664 bytes Bytes accessible per track: 55,996 bytes CI size: 4096 Physical record size: 4096 bytes Physical records per track (Bytes accessible per track / physical record size): 55,996 / 4096 = 13.6708984375 = 13 What I'm missing? Thanks! -- Oscar -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
W dniu 25.10.2021 o 16:44, Oscar pisze: Hi there, There's something I'm being missing, but acording to my numbers, there should be 13, not 12: Bytes per track: 56,664 bytes Bytes accessible per track: 55,996 bytes CI size: 4096 Physical record size: 4096 bytes Physical records per track (Bytes accessible per track / physical record size): 55,996 / 4096 = 13.6708984375 = 13 What I'm missing? You're missing CKD deep details. Instead of looking for old documentation just do some quick test: allocate single-track datasets. Each of them can be VSAM or just PS, it doesn't matter. However for PS it would be a little bit easier. Important: specify RECFM=F and LRECL=BLKSIZE=n, where n is any number you want to test. I would suggest the following: n=10 n=512 n=4096 Then use your ISPF editor to fill the datasets with some data. You will find out how many records/blocks fit on a track. Note: you won't get more than 86 blocks per track. Even very short ones. Reason? Gaps between blocks. More specifically: you block (physical records) consist of C and D. CKD is for Count Key Data. Your PS file has no K, so it is just C D. And gaps between them. And R0 which is also some physical record. And HA - Home Address, another 5-byte physical record. And 3390 is FBA under cover, with cell size=34B. And all the gaps or physical records (including C as separate entity) occupy one or more cells, not fraction. BTW: The above is part of "extra material" which I sometimes teach during VSAM course. -- Radoslaw Skorupka Lodz, Poland -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
Oscar, Here is a great Redbook for VSAM, enjoy. http://www.redbooks.ibm.com/abstracts/sg246105.html?Open Stay Safe > On Oct 25, 2021, at 10:54, Oscar wrote: > > Hi there, > > There's something I'm being missing, but acording to my numbers, there should > be 13, not 12: > > Bytes per track: 56,664 bytes > Bytes accessible per track: 55,996 bytes > CI size: 4096 > Physical record size: 4096 bytes > > Physical records per track (Bytes accessible per track / physical record > size): 55,996 / 4096 = 13.6708984375 = 13 > > What I'm missing? > > Thanks! > -- > Oscar > > -- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
Oscar, What you're missing is what used to be called the IRG (Inter Record Gap) on physical disk records. Now, on modern 3390 formatted disks, it is a more complicated calculation involving "cells," but it's the same idea; and only 12 4096 byte CIs will fit. Harry From: IBM Mainframe Discussion List on behalf of Oscar Sent: Monday, October 25, 2021 10:44 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13? Hi there, There's something I'm being missing, but acording to my numbers, there should be 13, not 12: Bytes per track: 56,664 bytes Bytes accessible per track: 55,996 bytes CI size: 4096 Physical record size: 4096 bytes Physical records per track (Bytes accessible per track / physical record size): 55,996 / 4096 = 13.6708984375 = 13 What I'm missing? Thanks! -- Oscar -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
Inter-record gaps between each physical block take space on the track away from data, not to mention count and key parts of each physical block (CKD means count-key-data). There is actually not any physical reason for IRG between physical blocks any more since we no longer have physical 33x0 devices (they are all virtual), but the concept is still implemented in the DASD controllers for compatibility. Peter -Original Message- From: IBM Mainframe Discussion List On Behalf Of Oscar Sent: Monday, October 25, 2021 10:44 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13? Hi there, There's something I'm being missing, but acording to my numbers, there should be 13, not 12: Bytes per track: 56,664 bytes Bytes accessible per track: 55,996 bytes CI size: 4096 Physical record size: 4096 bytes Physical records per track (Bytes accessible per track / physical record size): 55,996 / 4096 = 13.6708984375 = 13 What I'm missing? Thanks! -- This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
CA size and number of CI that fit in a CA Stay Safe > On Oct 25, 2021, at 10:54, Oscar wrote: > > Hi there, > > There's something I'm being missing, but acording to my numbers, there should > be 13, not 12: > > Bytes per track: 56,664 bytes > Bytes accessible per track: 55,996 bytes > CI size: 4096 > Physical record size: 4096 bytes > > Physical records per track (Bytes accessible per track / physical record > size): 55,996 / 4096 = 13.6708984375 = 13 > > What I'm missing? > > Thanks! > -- > Oscar > > -- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
VSAM: Why a CISIZE of 4KB has 12 phyrecs/Track, not 13?
Hi there, There's something I'm being missing, but acording to my numbers, there should be 13, not 12: Bytes per track: 56,664 bytes Bytes accessible per track: 55,996 bytes CI size: 4096 Physical record size: 4096 bytes Physical records per track (Bytes accessible per track / physical record size): 55,996 / 4096 = 13.6708984375 = 13 What I'm missing? Thanks! -- Oscar -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
