AW: Re: DB2 Locks and WLM Blocked Workload Support?
Excellent! Exactly the information I was looking for. Thank you, Horst and Greg. -- Peter Hunkeler -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
AW: Re: DB2 Locks and WLM Blocked Workload Support?
>If you have not done so, you might also want to post to the DB2 List who may >have more experience. First line of my post gives you the answer ;-) >>Cross-posted from DB2-L -- Peter Hunkeler -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: DB2 Locks and WLM Blocked Workload Support?
Peter, DB2 has the most comprehensive support to interact with WLM to address contention. DB2 will try to notify WLM about resource contention to extent it knows about dependencies. Based on such notifications DB2 and WLM support - Regular "enqueue promotion" and short term promotion . Both promote the holder of the lock to an elevated dispatch priority, increasing its chances to get dispatched. Search for "Sysevent ENQHOLD") - Chronic contention. Elevates the resource holder to the highest dispatch priority of any waiter. (Search for IWMCNTN). Still there can be situations where neither DB2 (and certainly no one else) knows the dependencies. For such cases the blocked workload support provides the capability that *any* address space that has been blocked -not dispatched- for a given time will be granted one time slice. That's a very small amount of processor time and it is handed out *independently* of any contention. Yet it is proven to be a very effective way to address DB2 latch contention. (Only latches typically gate such a short path that the contention can be resolved through one or a few of such "trickles".) See the ENV and BLWLINTHD IEAOPTxx parameter (BLWLTRPCT is almost never the limiting fact). Searching for OA44526 will give you a good list of recommendations. DB2 and GRS locks are unrelated (except for allocation related ones). Horst Sinram - STSM, IBM z/OS Workload and Capacity Management -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: DB2 Locks and WLM Blocked Workload Support?
On 2/6/2017 11:46 AM, Peter Hunkeler wrote: - Are the "DB2 latches" implemented as GRS latches? - Are row, page, tables space locks actually DB2 latches? In other words, would WLM be able to recognize a low priority job holding some DB2 locks is causeing delay so it can promote it? - What have IRLM and its lock structures to do with GRS latsches, if anything? - Does DB2 inform WLM about resource lockers, so WLM can possibly promote them? - DB2 does not use GRS latches. It has it's own internal latch manager. - Row, page, and table space locks are managed by IRLM for DB2. - IRLM does not use GRS latches. It has it's own internal latch manager. DB2 *will* communicate internal latch contention information to WLM. IRLM *will* communicate lock and internal latch contention information to WLM. Communication of contention information for WLM to take action with is not perfect. There are windows where sufficient information does not exist about the requestors. To cover these windows, WLM Blocked Workload support should always be enabled. Regards, Greg -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: DB2 Locks and WLM Blocked Workload Support?
If you have not done so, you might also want to post to the DB2 List who may have more experience. To join, if you have not so, go to IDUG.ORG Lizette -Original Message- >From: "van der Grijn, Bart (B)" <bvandergr...@dow.com> >Sent: Feb 6, 2017 11:09 AM >To: IBM-MAIN@LISTSERV.UA.EDU >Subject: Re: DB2 Locks and WLM Blocked Workload Support? > >Quick search yielded the following, which might help with some of your >questions: >https://www.toadworld.com/platforms/ibmdb2/b/weblog/archive/2013/04/22/db2-locking-part-3-locks-versus-latches >and >http://www-01.ibm.com/support/docview.wss?uid=swg1PM54608 > > >-Original Message- >From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On >Behalf Of Peter Hunkeler >Sent: Monday, February 06, 2017 12:47 PM >To: IBM-MAIN@LISTSERV.UA.EDU >Subject: DB2 Locks and WLM Blocked Workload Support? > > >Cross-posted from DB2-L > > >DB2 is not my strength, so please bear with me. > > >I understand that DB2 serializes access to its resources with various types of >locks. For access to data, some of them are row locks, page locks, tablespace >locks. > > >WLM's "blocked workload support" can help to reduce resource contention by >giving low priority, resource holding work a CPU burst, so it may release the >resource it held. > > >In the context of DB2, the doc talks about "DB2 latches" with which WLM may be >able to help. > > >Some (vague) questions. High level answers are sufficient. > > > > >- Are the "DB2 latches" implemented as GRS latches? > >- Are row, page, tables space locks actually DB2 latches? In other words, >would WLM be able to recognize a low priority job holding some DB2 locks is >causeing delay so it can promote it? > > >- What have IRLM and its lock structures to do with GRS latsches, if anything? > > >- Does DB2 inform WLM about resource lockers, so WLM can possibly promote them? > > > >Pointer to some documentation if I can answer myself by RTFM is appreciated. > > >-- >Peter Hunkeler -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
Re: DB2 Locks and WLM Blocked Workload Support?
Quick search yielded the following, which might help with some of your questions: https://www.toadworld.com/platforms/ibmdb2/b/weblog/archive/2013/04/22/db2-locking-part-3-locks-versus-latches and http://www-01.ibm.com/support/docview.wss?uid=swg1PM54608 -Original Message- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Peter Hunkeler Sent: Monday, February 06, 2017 12:47 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: DB2 Locks and WLM Blocked Workload Support? Cross-posted from DB2-L DB2 is not my strength, so please bear with me. I understand that DB2 serializes access to its resources with various types of locks. For access to data, some of them are row locks, page locks, tablespace locks. WLM's "blocked workload support" can help to reduce resource contention by giving low priority, resource holding work a CPU burst, so it may release the resource it held. In the context of DB2, the doc talks about "DB2 latches" with which WLM may be able to help. Some (vague) questions. High level answers are sufficient. - Are the "DB2 latches" implemented as GRS latches? - Are row, page, tables space locks actually DB2 latches? In other words, would WLM be able to recognize a low priority job holding some DB2 locks is causeing delay so it can promote it? - What have IRLM and its lock structures to do with GRS latsches, if anything? - Does DB2 inform WLM about resource lockers, so WLM can possibly promote them? Pointer to some documentation if I can answer myself by RTFM is appreciated. -- Peter Hunkeler -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
