Re: ALTER of open VSAM cluster
Joel, On 07/30/2010 08:57 AM, John H Kington wrote: David, Please see 2.5.3.2 Altering the Free Space Specification When Loading a Data Set in z/OS V1R11 DFSMS Using Data Sets for a definitive answer. The manual does state the file needs to be closed for the new Freespace values to take effect. Spot on. The freespace parameter is only used for loading the vsam file. If anyone cares to read the section that David referenced, it discusses loading a portion of the records, closing the file, altering the freespace, loading more records and so forth. Freespace is not used in CI or CA split processing. Learned something new. I was not aware that load process could be trivially split into multiple REPRO steps with a change of freespace before each. It would only make sense in special cases where you know some specific blocks of records are subject to update activity and others are not. Once the sequential load process is done, adding/updating records that result in CI/CA splits proceeds without regard to freespace. Me too. It is wonderful what you can learn when you read the fine manual! One thing that is still not clear to me from the wording of that excerpt: can you at an arbitrary time in the life of a KSDS open the data set for sequential output and append an ordered block of additional higher key records to the end of the file that are written subject to the current freespace specification? In other words is there really such a thing as a load state for KSDS or is it just that when multiple ordered records are being written with sequential output and the keys start beyond the highest current key value that this is an instance of loading the file? I wish I still had access to a mainframe to observe and verify. I would have sworn that you could only do a load in one shot and that you were stuck using the same freespace parameters through-out the entire vsam file. Kudos to IBM for a clear and interesting example. Regards, John NOTICE: The information contained in this electronic mail transmission is intended by Convergys Corporation for the use of the named individual or entity to which it is directed and may contain information that is privileged or otherwise confidential. If you have received this electronic mail transmission in error, please delete it from your system without copying or forwarding it, and notify the sender of the error by reply email or by telephone (collect), so that the sender's address records can be corrected. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
Frank, Interesting comment on the original define. We don't save our original defines; nor do we generally do a DELETE/DEFINE when we reload a file. We always (except when not allowed; ie AIX) use REUSE. It could be my paranoia, but think in terms of file deletion, accidental or otherwise. It would be handy to have the define somewhere instead of having to discover them. Regards, John NOTICE: The information contained in this electronic mail transmission is intended by Convergys Corporation for the use of the named individual or entity to which it is directed and may contain information that is privileged or otherwise confidential. If you have received this electronic mail transmission in error, please delete it from your system without copying or forwarding it, and notify the sender of the error by reply email or by telephone (collect), so that the sender's address records can be corrected. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
On 7/29/2010 at 7:53 PM, in message 4c5230b4.2010...@acm.org, Joel C. Ewing jcew...@acm.org wrote: On 07/29/2010 06:26 PM, Thompson, Steve wrote: -Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Frank Swarbrick Sent: Thursday, July 29, 2010 5:53 PM To: IBM-MAIN@bama.ua.edu Subject: ALTER of open VSAM cluster It appears we can ALTER FREESPACE while a file is open to CICS (or anywhere else, I assume). Is this an OK thing to do, so the next time the file is reloaded it will use the new freespace values? SNIP The ALTER modifies the definition info in the Catalog (as I recall). So the effect is rather immediate. What this will do is allow you to LOAD with x y for freespace, and then when running change to m n for freespace. So, let us say that you LOAD a KSDS with FREESPACE(0 0) that has 50 CYLs of data. Once the load is complete you ALTER it to FREESPACE(25 25). You know that the majority of the adds to the file will start in the last 2 cylinders of data (as loaded) and go from there. So the CA/CI splits will start at that point. Regards, Steve Thompson ... Steve, If you are implying that changing FREESPACE of a loaded file will affect future adds at the high end of the key range, this is not true. Changing FREESPACE has no effect on a VSAM file already containing records. FREESPACE is only used when the file is in a reset or initial empty state with no records and an initial file load is done. I am also certain that if you could ALTER the VSAM catalog entry while the file is still OPEN for that initial load process, that the running program doing the load is at that point only using in-memory control blocks for the VSAM file with values that were derived at OPEN time, and only future OPENS would see any change. After that intial load, adding a record than doesn't fit in an existing CI results in a CI split with about half the CI records going to a new CI, and if there are no free CI's in that CA, a CA-split is first done to put about half of that CA's CI's in a new CA. The FREESPACE is totally ignored in that process. Even if all the future adds have ascending key values, the add logic is the same. Unless you define the VSAM file with REUSE and have an application that resets the file to empty and reloads all records at some later time without deleting and redefining the dataset, changing FREESPACE after initial load would have no effect. CI splits are relatively cheap, so using CI FREESPACE to minimize CI-splits after initial load has minimal benefit and in cases where a large percent of records must be read may actually reduce performance by requiring reading of more CIs to get the same data. CA-splits are relatively expensive, so there may be special cases where CA-FREESPACE can improve update response consistency after an initial load. But even with FREESPACE(0,0), if updates are clustered by key, performance will improve after the initial CI and CA splits from earlier updates introduce free space at the precise points in the file undergoing repeated changes. Here are the details on the file in question. I just did a CLO ENA in CICS to get update VSAM stats: ATTRIBUTES KEYLEN-9 AVGLRECL-250 BUFSPACE---15872 CISIZE--7168 RKP0 MAXLRECL1900 EXCPEXIT--(NULL) CI/CA105 SHROPTNS(2,3) SPEED UNIQUE NOERASE INDEXED NOWRITECHK NOIMBED NOREPLICAT UNORDERED REUSE NONSPANNED STATISTICS REC-TOTAL-791636 SPLITS-CI---8135 EXCPS1125532 REC-DELETED0 SPLITS-CA228 EXTENTS1 REC-INSERTED---9 FREESPACE-%CI--0 SYSTEM-TIMESTAMP: REC-UPDATED---659805 FREESPACE-%CA--0 X'C65CE0AD26274284' REC-RETRIEVED2903925 FREESPC146055168 The file is REUSE and is reloaded at the beginning of every business day. (So as of the above stats it's been open about 24 hours.) The end of each record is a transaction table that contains up to 20 transactions per day. In other words, as the customer has new transactions the length of the record is extended to allow for this new record and then the record is rewritten. Updates are random (not clustered). When we were on VSE I think we
Re: ALTER of open VSAM cluster
On 7/30/2010 at 5:56 AM, in message 23b13969513a9846a621a4620543d4f977119da...@cdcmw12e.na.convergys.com, John H Kington john.king...@convergys.com wrote: Frank, It appears we can ALTER FREESPACE while a file is open to CICS (or anywhere else, I assume). Is this an OK thing to do, so the next time the file is reloaded it will use the new freespace values? Altering the freespace parameters on a loaded vsam file will not have any effect. If the vsam file has the REUSE attribute and you reload the file, the new freespace parameters will be honored. Be sure to change the freespace parameters on the original define in case you do a delete, define and reload of the vsam file. This is exactly what I want. Interesting comment on the original define. We don't save our original defines; nor do we generally do a DELETE/DEFINE when we reload a file. We always (except when not allowed; ie AIX) use REUSE. Thanks, Frank -- Frank Swarbrick Applications Architect - Mainframe Applications Development FirstBank Data Corporation - Lakewood, CO USA P: 303-235-1403 The information contained in this electronic communication and any document attached hereto or transmitted herewith is confidential and intended for the exclusive use of the individual or entity named above. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that any examination, use, dissemination, distribution or copying of this communication or any part thereof is strictly prohibited. If you have received this communication in error, please immediately notify the sender by reply e-mail and destroy this communication. Thank you. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
No wonder I couldn't find it. I was looking under ALTER in DFSMS Access Method Services for Catalogs and could fine no mention of when it would take affect. On 7/30/2010 at 7:52 AM, in message cd22aa1aee707d489d9250d13e3862a1858765b...@nihmlbxcms02.nih.gov, O'Brien, David W. (NIH/CIT) [C] obrie...@mail.nih.gov wrote: Please see 2.5.3.2 Altering the Free Space Specification When Loading a Data Set in z/OS V1R11 DFSMS Using Data Sets for a definitive answer. The manual does state the file needs to be closed for the new Freespace values to take effect. Thank You, Dave O'Brien NIH Contractor From: Thompson, Steve [steve_thomp...@stercomm.com] Sent: Friday, July 30, 2010 9:41 AM To: IBM-MAIN@bama.ua.edu Subject: Re: ALTER of open VSAM cluster -Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Joel C. Ewing Sent: Thursday, July 29, 2010 8:54 PM To: IBM-MAIN@bama.ua.edu Subject: Re: ALTER of open VSAM cluster SNIPPAGE ... Steve, If you are implying that changing FREESPACE of a loaded file will affect future adds at the high end of the key range, this is not true. Changing FREESPACE has no effect on a VSAM file already containing records. FREESPACE is only used when the file is in a reset or initial empty state with no records and an initial file load is done. I am also certain that if you could ALTER the VSAM catalog entry while the file is still OPEN for that initial load process, that the running program doing the load is at that point only using in-memory control blocks for the VSAM file with values that were derived at OPEN time, and only future OPENS would see any change. SNIP Unless something has changed since z/OS 1.1, and a third party product would give new behaviors -- even when not being directly invoked, that is exactly what we did at a certain insurance type company for their customer claims file. It was laid down with NO freespace. Then it was altered pretty much the way I said. The CICS system was brought up after the ALTER (which is why I said the catalog info was changed -- I didn't mean to imply an open file would get this behavior without an intervening close). Meanwhile, I was interpreting the original op's question on the basis of the alter being done for current operations, not later reloading the file. Yes, in that case the file must be defined with REUSE. SNIP Regards, Steve Thompson -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html The information contained in this electronic communication and any document attached hereto or transmitted herewith is confidential and intended for the exclusive use of the individual or entity named above. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that any examination, use, dissemination, distribution or copying of this communication or any part thereof is strictly prohibited. If you have received this communication in error, please immediately notify the sender by reply e-mail and destroy this communication. Thank you. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
All, It seems we have several versions of how Freespace operates in a KSDS. I recall that FreeSpace was maintained when records are inserted at the end of file, but not SIS. I found the following reference at http://www.slideshare.net/danjodea/basic-vsam.; When records are inserted between existing records and there's not enough free space, CI and maybe CA splits occur to fit the new record. If records are being inserted at the end of a file, free space is reserved as records are added (a resume load) I also recall the ALTER FRSPC technique after loading a KSDS as valid strategy, but I don't think I ever used it. However, if KSDS processing has change then it may have to be relegated to the superseded bucket. Ron -Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of R.S. Sent: Friday, July 30, 2010 1:03 PM To: IBM-MAIN@bama.ua.edu Subject: Re: [IBM-MAIN] ALTER of open VSAM cluster W dniu 2010-07-30 19:57, Joel C. Ewing pisze: On 07/30/2010 08:57 AM, John H Kington wrote: David, Please see 2.5.3.2 Altering the Free Space Specification When Loading a Data Set in z/OS V1R11 DFSMS Using Data Sets for a definitive answer. The manual does state the file needs to be closed for the new Freespace values to take effect. Spot on. The freespace parameter is only used for loading the vsam file. If anyone cares to read the section that David referenced, it discusses loading a portion of the records, closing the file, altering the freespace, loading more records and so forth. Freespace is not used in CI or CA split processing. Regards, John Learned something new. I was not aware that load process could be trivially split into multiple REPRO steps with a change of freespace before each. It would only make sense in special cases where you know some specific blocks of records are subject to update activity and others are not. Well, IMHO it's well known trick. (Well known? Are VSAMs well know? vbg) BTW: The reasons for such tricks changed over the years. Nowadays we shouldn't care if your VSAM *is already* fragmented (splitted CIs and CAs). Usually it doesn't affect performance, *except* the moment of split. THe same apply to disk space - reclamation of overallocated space is not an issue. Once the sequential load process is done, adding/updating records that result in CI/CA splits proceeds without regard to freespace. It depends on the process! One thing that is still not clear to me from the wording of that excerpt: can you at an arbitrary time in the life of a KSDS open the data set for sequential output and append an ordered block of additional higher key records to the end of the file that are written subject to the current freespace specification? In other words is there really such a thing as a load state for KSDS or is it just that when multiple ordered records are being written with sequential output and the keys start beyond the highest current key value that this is an instance of loading the file? Re-read your own statement. First load, change FSPC, second LOAD, and so on. More than one load is possible. What's impossible is SPEED vs RECOVERY processing. It's a choice for very first load only. -- Radoslaw Skorupka Lodz, Poland -- BRE Bank SA ul. Senatorska 18 00-950 Warszawa www.brebank.pl Sd Rejonowy dla m. st. Warszawy XII Wydzia Gospodarczy Krajowego Rejestru Sdowego, nr rejestru przedsibiorców KRS 025237 NIP: 526-021-50-88 Wedug stanu na dzie 01.01.2009 r. kapita zakadowy BRE Banku SA (w caoci wpacony) wynosi 118.763.528 zotych. W zwizku z realizacj warunkowego podwyszenia kapitau zakadowego, na podstawie uchway XXI WZ z dnia 16 marca 2008r., oraz uchway XVI NWZ z dnia 27 padziernika 2008r., moe ulec podwyszeniu do kwoty 123.763.528 z. Akcje w podwyszonym kapitale zakadowym BRE Banku SA bd w caoci opacone. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
Frank, It appears we can ALTER FREESPACE while a file is open to CICS (or anywhere else, I assume). Is this an OK thing to do, so the next time the file is reloaded it will use the new freespace values? Altering the freespace parameters on a loaded vsam file will not have any effect. If the vsam file has the REUSE attribute and you reload the file, the new freespace parameters will be honored. Be sure to change the freespace parameters on the original define in case you do a delete, define and reload of the vsam file. Regards, John NOTICE: The information contained in this electronic mail transmission is intended by Convergys Corporation for the use of the named individual or entity to which it is directed and may contain information that is privileged or otherwise confidential. If you have received this electronic mail transmission in error, please delete it from your system without copying or forwarding it, and notify the sender of the error by reply email or by telephone (collect), so that the sender's address records can be corrected. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
Frank, Perhaps it would be helpful if you described what you were trying to accomplish by changing the Freespace after the initial load. Any change would only affect the CA/CI splits after the change. If you then use Export/Import to re-org the file, the new Freespace values are honored. Using Delete/Define/re-load without changing the original define parameters would revert Freespace back to the original values. Thank You, Dave O'Brien NIH Contractor From: John H Kington [john.king...@convergys.com] Sent: Friday, July 30, 2010 7:56 AM To: IBM-MAIN@bama.ua.edu Subject: Re: ALTER of open VSAM cluster Frank, It appears we can ALTER FREESPACE while a file is open to CICS (or anywhere else, I assume). Is this an OK thing to do, so the next time the file is reloaded it will use the new freespace values? Altering the freespace parameters on a loaded vsam file will not have any effect. If the vsam file has the REUSE attribute and you reload the file, the new freespace parameters will be honored. Be sure to change the freespace parameters on the original define in case you do a delete, define and reload of the vsam file. Regards, John NOTICE: The information contained in this electronic mail transmission is intended by Convergys Corporation for the use of the named individual or entity to which it is directed and may contain information that is privileged or otherwise confidential. If you have received this electronic mail transmission in error, please delete it from your system without copying or forwarding it, and notify the sender of the error by reply email or by telephone (collect), so that the sender's address records can be corrected. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
-Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Joel C. Ewing Sent: Thursday, July 29, 2010 8:54 PM To: IBM-MAIN@bama.ua.edu Subject: Re: ALTER of open VSAM cluster SNIPPAGE ... Steve, If you are implying that changing FREESPACE of a loaded file will affect future adds at the high end of the key range, this is not true. Changing FREESPACE has no effect on a VSAM file already containing records. FREESPACE is only used when the file is in a reset or initial empty state with no records and an initial file load is done. I am also certain that if you could ALTER the VSAM catalog entry while the file is still OPEN for that initial load process, that the running program doing the load is at that point only using in-memory control blocks for the VSAM file with values that were derived at OPEN time, and only future OPENS would see any change. SNIP Unless something has changed since z/OS 1.1, and a third party product would give new behaviors -- even when not being directly invoked, that is exactly what we did at a certain insurance type company for their customer claims file. It was laid down with NO freespace. Then it was altered pretty much the way I said. The CICS system was brought up after the ALTER (which is why I said the catalog info was changed -- I didn't mean to imply an open file would get this behavior without an intervening close). Meanwhile, I was interpreting the original op's question on the basis of the alter being done for current operations, not later reloading the file. Yes, in that case the file must be defined with REUSE. SNIP Regards, Steve Thompson -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
Please see 2.5.3.2 Altering the Free Space Specification When Loading a Data Set in z/OS V1R11 DFSMS Using Data Sets for a definitive answer. The manual does state the file needs to be closed for the new Freespace values to take effect. Thank You, Dave O'Brien NIH Contractor From: Thompson, Steve [steve_thomp...@stercomm.com] Sent: Friday, July 30, 2010 9:41 AM To: IBM-MAIN@bama.ua.edu Subject: Re: ALTER of open VSAM cluster -Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Joel C. Ewing Sent: Thursday, July 29, 2010 8:54 PM To: IBM-MAIN@bama.ua.edu Subject: Re: ALTER of open VSAM cluster SNIPPAGE ... Steve, If you are implying that changing FREESPACE of a loaded file will affect future adds at the high end of the key range, this is not true. Changing FREESPACE has no effect on a VSAM file already containing records. FREESPACE is only used when the file is in a reset or initial empty state with no records and an initial file load is done. I am also certain that if you could ALTER the VSAM catalog entry while the file is still OPEN for that initial load process, that the running program doing the load is at that point only using in-memory control blocks for the VSAM file with values that were derived at OPEN time, and only future OPENS would see any change. SNIP Unless something has changed since z/OS 1.1, and a third party product would give new behaviors -- even when not being directly invoked, that is exactly what we did at a certain insurance type company for their customer claims file. It was laid down with NO freespace. Then it was altered pretty much the way I said. The CICS system was brought up after the ALTER (which is why I said the catalog info was changed -- I didn't mean to imply an open file would get this behavior without an intervening close). Meanwhile, I was interpreting the original op's question on the basis of the alter being done for current operations, not later reloading the file. Yes, in that case the file must be defined with REUSE. SNIP Regards, Steve Thompson -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
-Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Thompson, Steve Sent: Friday, July 30, 2010 8:42 AM To: IBM-MAIN@bama.ua.edu Subject: Re: ALTER of open VSAM cluster -Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Joel C. Ewing Sent: Thursday, July 29, 2010 8:54 PM To: IBM-MAIN@bama.ua.edu Subject: Re: ALTER of open VSAM cluster SNIPPAGE ... Steve, If you are implying that changing FREESPACE of a loaded file will affect future adds at the high end of the key range, this is not true. Changing FREESPACE has no effect on a VSAM file already containing records. FREESPACE is only used when the file is in a reset or initial empty state with no records and an initial file load is done. I am also certain that if you could ALTER the VSAM catalog entry while the file is still OPEN for that initial load process, that the running program doing the load is at that point only using in-memory control blocks for the VSAM file with values that were derived at OPEN time, and only future OPENS would see any change. SNIP Unless something has changed since z/OS 1.1, and a third party product would give new behaviors -- even when not being directly invoked, that is exactly what we did at a certain insurance type company for their customer claims file. It was laid down with NO freespace. Then it was altered pretty much the way I said. The CICS system was brought up after the ALTER (which is why I said the catalog info was changed -- I didn't mean to imply an open file would get this behavior without an intervening close). Meanwhile, I was interpreting the original op's question on the basis of the alter being done for current operations, not later reloading the file. Yes, in that case the file must be defined with REUSE. SNIP Well, I went back to my trusty IDCAMS manual from z/OS 1.7 to capture a little tid-bit from the ALTER command and its FREESPACE write-up. And here is what I found, that somehow I had not ever seen before. If the FREESPACE is altered after the data set has been loaded, and sequential insert processing is used, the allocation of free space is not honored. So, if any one wants my address, I'm in the process of another helping of humble pie with a side of crow. And I imagine a few more helpings might be on the way. I sure hope those guys that set that up at that company read this little tid-bit, because we all were under the impression that we had solved a performance problem with this. It sure seemed that way anyhow. Regards, Steve Thompson Ps. Nothing like crow for breakfast. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
David, Please see 2.5.3.2 Altering the Free Space Specification When Loading a Data Set in z/OS V1R11 DFSMS Using Data Sets for a definitive answer. The manual does state the file needs to be closed for the new Freespace values to take effect. Spot on. The freespace parameter is only used for loading the vsam file. If anyone cares to read the section that David referenced, it discusses loading a portion of the records, closing the file, altering the freespace, loading more records and so forth. Freespace is not used in CI or CA split processing. Regards, John NOTICE: The information contained in this electronic mail transmission is intended by Convergys Corporation for the use of the named individual or entity to which it is directed and may contain information that is privileged or otherwise confidential. If you have received this electronic mail transmission in error, please delete it from your system without copying or forwarding it, and notify the sender of the error by reply email or by telephone (collect), so that the sender's address records can be corrected. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
On 07/30/2010 08:57 AM, John H Kington wrote: David, Please see 2.5.3.2 Altering the Free Space Specification When Loading a Data Set in z/OS V1R11 DFSMS Using Data Sets for a definitive answer. The manual does state the file needs to be closed for the new Freespace values to take effect. Spot on. The freespace parameter is only used for loading the vsam file. If anyone cares to read the section that David referenced, it discusses loading a portion of the records, closing the file, altering the freespace, loading more records and so forth. Freespace is not used in CI or CA split processing. Regards, John Learned something new. I was not aware that load process could be trivially split into multiple REPRO steps with a change of freespace before each. It would only make sense in special cases where you know some specific blocks of records are subject to update activity and others are not. Once the sequential load process is done, adding/updating records that result in CI/CA splits proceeds without regard to freespace. One thing that is still not clear to me from the wording of that excerpt: can you at an arbitrary time in the life of a KSDS open the data set for sequential output and append an ordered block of additional higher key records to the end of the file that are written subject to the current freespace specification? In other words is there really such a thing as a load state for KSDS or is it just that when multiple ordered records are being written with sequential output and the keys start beyond the highest current key value that this is an instance of loading the file? -- Joel C. Ewing, Fort Smith, ARjcew...@acm.org -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
W dniu 2010-07-30 19:57, Joel C. Ewing pisze: On 07/30/2010 08:57 AM, John H Kington wrote: David, Please see 2.5.3.2 Altering the Free Space Specification When Loading a Data Set in z/OS V1R11 DFSMS Using Data Sets for a definitive answer. The manual does state the file needs to be closed for the new Freespace values to take effect. Spot on. The freespace parameter is only used for loading the vsam file. If anyone cares to read the section that David referenced, it discusses loading a portion of the records, closing the file, altering the freespace, loading more records and so forth. Freespace is not used in CI or CA split processing. Regards, John Learned something new. I was not aware that load process could be trivially split into multiple REPRO steps with a change of freespace before each. It would only make sense in special cases where you know some specific blocks of records are subject to update activity and others are not. Well, IMHO it's well known trick. (Well known? Are VSAMs well know? vbg) BTW: The reasons for such tricks changed over the years. Nowadays we shouldn't care if your VSAM *is already* fragmented (splitted CIs and CAs). Usually it doesn't affect performance, *except* the moment of split. THe same apply to disk space - reclamation of overallocated space is not an issue. Once the sequential load process is done, adding/updating records that result in CI/CA splits proceeds without regard to freespace. It depends on the process! One thing that is still not clear to me from the wording of that excerpt: can you at an arbitrary time in the life of a KSDS open the data set for sequential output and append an ordered block of additional higher key records to the end of the file that are written subject to the current freespace specification? In other words is there really such a thing as a load state for KSDS or is it just that when multiple ordered records are being written with sequential output and the keys start beyond the highest current key value that this is an instance of loading the file? Re-read your own statement. First load, change FSPC, second LOAD, and so on. More than one load is possible. What's impossible is SPEED vs RECOVERY processing. It's a choice for very first load only. -- Radoslaw Skorupka Lodz, Poland -- BRE Bank SA ul. Senatorska 18 00-950 Warszawa www.brebank.pl Sd Rejonowy dla m. st. Warszawy XII Wydzia Gospodarczy Krajowego Rejestru Sdowego, nr rejestru przedsibiorców KRS 025237 NIP: 526-021-50-88 Wedug stanu na dzie 01.01.2009 r. kapita zakadowy BRE Banku SA (w caoci wpacony) wynosi 118.763.528 zotych. W zwizku z realizacj warunkowego podwyszenia kapitau zakadowego, na podstawie uchway XXI WZ z dnia 16 marca 2008r., oraz uchway XVI NWZ z dnia 27 padziernika 2008r., moe ulec podwyszeniu do kwoty 123.763.528 z. Akcje w podwyszonym kapitale zakadowym BRE Banku SA bd w caoci opacone. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
ALTER of open VSAM cluster
It appears we can ALTER FREESPACE while a file is open to CICS (or anywhere else, I assume). Is this an OK thing to do, so the next time the file is reloaded it will use the new freespace values? -- Frank Swarbrick Applications Architect - Mainframe Applications Development FirstBank Data Corporation - Lakewood, CO USA P: 303-235-1403 The information contained in this electronic communication and any document attached hereto or transmitted herewith is confidential and intended for the exclusive use of the individual or entity named above. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that any examination, use, dissemination, distribution or copying of this communication or any part thereof is strictly prohibited. If you have received this communication in error, please immediately notify the sender by reply e-mail and destroy this communication. Thank you. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
-Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Frank Swarbrick Sent: Thursday, July 29, 2010 5:53 PM To: IBM-MAIN@bama.ua.edu Subject: ALTER of open VSAM cluster It appears we can ALTER FREESPACE while a file is open to CICS (or anywhere else, I assume). Is this an OK thing to do, so the next time the file is reloaded it will use the new freespace values? SNIP The ALTER modifies the definition info in the Catalog (as I recall). So the effect is rather immediate. What this will do is allow you to LOAD with x y for freespace, and then when running change to m n for freespace. So, let us say that you LOAD a KSDS with FREESPACE(0 0) that has 50 CYLs of data. Once the load is complete you ALTER it to FREESPACE(25 25). You know that the majority of the adds to the file will start in the last 2 cylinders of data (as loaded) and go from there. So the CA/CI splits will start at that point. Regards, Steve Thompson -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: ALTER of open VSAM cluster
On 07/29/2010 06:26 PM, Thompson, Steve wrote: -Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Frank Swarbrick Sent: Thursday, July 29, 2010 5:53 PM To: IBM-MAIN@bama.ua.edu Subject: ALTER of open VSAM cluster It appears we can ALTER FREESPACE while a file is open to CICS (or anywhere else, I assume). Is this an OK thing to do, so the next time the file is reloaded it will use the new freespace values? SNIP The ALTER modifies the definition info in the Catalog (as I recall). So the effect is rather immediate. What this will do is allow you to LOAD with x y for freespace, and then when running change to m n for freespace. So, let us say that you LOAD a KSDS with FREESPACE(0 0) that has 50 CYLs of data. Once the load is complete you ALTER it to FREESPACE(25 25). You know that the majority of the adds to the file will start in the last 2 cylinders of data (as loaded) and go from there. So the CA/CI splits will start at that point. Regards, Steve Thompson ... Steve, If you are implying that changing FREESPACE of a loaded file will affect future adds at the high end of the key range, this is not true. Changing FREESPACE has no effect on a VSAM file already containing records. FREESPACE is only used when the file is in a reset or initial empty state with no records and an initial file load is done. I am also certain that if you could ALTER the VSAM catalog entry while the file is still OPEN for that initial load process, that the running program doing the load is at that point only using in-memory control blocks for the VSAM file with values that were derived at OPEN time, and only future OPENS would see any change. After that intial load, adding a record than doesn't fit in an existing CI results in a CI split with about half the CI records going to a new CI, and if there are no free CI's in that CA, a CA-split is first done to put about half of that CA's CI's in a new CA. The FREESPACE is totally ignored in that process. Even if all the future adds have ascending key values, the add logic is the same. Unless you define the VSAM file with REUSE and have an application that resets the file to empty and reloads all records at some later time without deleting and redefining the dataset, changing FREESPACE after initial load would have no effect. CI splits are relatively cheap, so using CI FREESPACE to minimize CI-splits after initial load has minimal benefit and in cases where a large percent of records must be read may actually reduce performance by requiring reading of more CIs to get the same data. CA-splits are relatively expensive, so there may be special cases where CA-FREESPACE can improve update response consistency after an initial load. But even with FREESPACE(0,0), if updates are clustered by key, performance will improve after the initial CI and CA splits from earlier updates introduce free space at the precise points in the file undergoing repeated changes. -- Joel C. Ewing, Fort Smith, ARjcew...@acm.org -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
