I recently communicated with a Db2 for z/OS system administrator who had some concerns about non-universal table spaces in the context of his organization's planned migration from Db2 12 to Db2 13. This person asked important questions about the presence of non-universal table spaces in his Db2 environment and how those database objects might affect his team's plans for Db2 12-to-13 migration. Looking over that communications thread, I found myself thinking (as I often have over the years) that it could be the basis for a blog entry that would be helpful for people in the wider Db2 for z/OS us ..read more

At this writing, a lot of Db2 for z/OS-using organizations are actively engaged in migrating to Db2 13 from Db2 12, and plenty of sites have recently gotten to Db2 13. That being the case, it seems like a good time to remind people of an important step to take after migrating to Db2 13, while still at the V13R1M100 function level (the initial Db2 13 function level when you've migrated from Db2 12): rebind all your plans and packages. First: why do this? For a couple of reasons. One would be to get a CPU efficiency benefit. The other has to do with the benefit of keeping package code current (I ..read more

What I'm writing about today is something I've been talking about for years, thought often in a somewhat indirect way. It has to do with mainframe memory (often referred to as "real storage" by z/OS people, to distinguish it from virtual storage) - more specifically, what it takes, memory-wise, to have what I'd call a balanced configuration for a z/OS LPAR (a z/OS LPAR, or logical partition, is a z/OS system; Db2 for z/OS runs within a z/OS LPAR, and a given mainframe "box" could house one or more z/OS LPARs). After working this year with a couple of situations involving z/OS LPARs with not-we ..read more

It's pretty well known that getting the activated function level of a Db2 12 for z/OS system to V12R1M510 is required prior to migrating that Db2 12 system to Db2 13 (I blogged about that a couple of years ago). At present (June, 2024), there are still a good number of sites running Db2 12 for z/OS with an activated function level of V12R1M500. I sometimes get, from people at such sites, a question like this: "How should we go from Db2 12 function level 500 to function level 510?" Generally speaking, what these folks are wanting is for me to opine on going straight from Db2 12 function level 5 ..read more

 Back in 2018, I reviewed an organization's production Db2 for z/OS environment, and saw at that time the largest z/OS LPAR real storage size I'd ever seen: 1100 GB. The Db2 subsystem running in that LPAR had (not surprisingly) the largest buffer pool configuration I'd ever seen: 879 GB (referring to the aggregate size of all of the Db2 subsystem's buffer pools). Within that buffer pool configuration was (again, not surprising) the lagest single Db2 buffer pool I'd ever seen: approximately 262 GB (66,500,000 4K buffers). Those "biggest I've ever seen" figures sustained that status until j ..read more

 A few months ago, I got this question from a Db2 for z/OS DBA: "Is there a way we can check to see if the UNLOAD utility has been executed for certain of our tables?" The environment in question was a Db2 12 for z/OS system, and because of that I had to provide an answer that was less-than-great from an ease-of-use persepective: "Yes, you can do that in a Db2 12 environment, but the process is going to be a bit cumbersome. You could set up a Db2 audit policy that would record utility execution. What that will do is cause Db2 to write certain trace records when utilities are executed ..read more

Not long ago, a Db2 for z/OS DBA sent to me, via a colleague of mine, a question. He described in an email the procedure that his team regularly used to consolidate extents, when the number of these got into double digits for a Db2 table space-related data set, back down to one. He noted that this extent-consolidation procedure was more time-consuming and CPU-intensive than desired, and he wanted to know if I had any suggestions for making the procedure more efficient. In fact, I did have a suggestion for improving the efficiency of the Db2 data set extent consolidation procedure used at this ..read more

The APPLCOMPAT option of the Db2 for z/OS BIND and REBIND PACKAGE commands is really important - that's why I posted part 1 and part 2 blog entries on the topic back in 2019. The APPLCOMPAT parameter in ZPARM, on the other hand (referring to DSNZPARM, the data set that contains a Db2 subsystem's configuration parameter settings), is less important. I pointed this out in part 1 of the aforementioned two-part blog entry on APPLCOMPAT, but I still find that plenty of Db2 for z/OS people ascribe significance to the ZPARM parameter APPLCOMPAT that just doesn't jibe with reality. That being the case ..read more

In a Db2 for z/OS context, the terms "code level," "catalog level," and "function level" were introduced when the Db2 for z/OS development team went to the continuous delivery mechanism for delivering new product functionality in-between the availability dates of new versions of the DBMS. That was a little over 7 years ago, referring to the general availability of Db2 12 - the first continuous-delivery version of Db2 for z/OS. And yet, there remains a good bit of misunderstanding among some in the Db2 for z/OS user community regarding basic concepts that are of foundational importance in a con ..read more

Db2 13 function level 504 became available last month (October 2023), via the fix for APAR PH54919. One of the new capabilities delivered with FL504 is something called autobind phase-in. I like that new feature a lot, and I think you will, too - especially if you're a Db2 for z/OS DBA. In this blog entry I'll explain what autobind phase-in is, why it's a very welcome addition to Db2 functionality, and how you can get ready to leverage the feature, even before you've activated function level V13R1M504. First, a shout-out to my coworker Dengfeng Gao, a member of the IBM Db2 for z/OS develo ..read more