Peggy Zagelow - a view from the lab
I've received a few questions about text search in DB2 9 for z/OS lately, so I thought I'd share the basic information here.
Prior to DB2 9, there was an offering called "DB2 Text Extender". This was an early attempt at text indexing that runs on z/OS. It is dependent on some z/OS code called "Text Search". Later on, the team that worked on the extenders also released something called "DB2 Net Search Extender", aka NSE. DB2 for Linux, Unix, and Windows had a significant upgrade with NSE, but that same upgrade was not shipped for DB2 for z/OS. So DB2 for z/OS customers have not had a significant upgrade to text search since "DB2 Text Extender" in DB2 V7.
In DB2 9, there is a completely new text search solution. Text search is provided by a built-in engine function called CONTAINS. This solution requires an external text search server that runs on a Windows or Linux operating system, which is provided as part of the DB2 Accessories suite. It is not a direct replacement of Text Extender function, so applications and administration policies need to be updated for this change. The best source for detailed information about this is in the information center topic Administering IBM text search for DB2 for z/OS. And I have an earlier blog entry about the announcement.
What about the DB2 Text Extender? It's not available in DB2 9 for z/OS. That means you won't see an equivalent for DB2 V8 FMID JDB881C. And you won't need IBM Text Search FMID-HIMN230 in DB2 9 for z/OS either, because that was a prerequisite for the DB2 Text Extender.
The above is all specific to DB2 for z/OS. DB2 for LUW 9.5 FP 1 ships the same Omnifind text search server, and DB2 LUW still ships support for their NSE as well.
Now that we've got that all cleared up :-), next we'll evaluate some use cases for text search applicability.[Read More]
I was pointed to this interesting article from the New York Times, about a new technology invented by two software engineers, Jonathan Lindo and Jeffrey Daudel, to be able to "replay" the events that led up to a system crash. Not that I really want to see my "blue screen of death" from yesterday again, but if it would help identify the problem and get a fix, I could probably live through it a couple more times.
Reading the article, I was struck by a couple of points. They quote Lindo as saying that the inspiration came to them as "Wouldn't it be great if we could just TiVo this and replay it?" And then it says this:
Innovation by analogy is a powerful concept, says Giovanni Gavetti, an associate professor at the Harvard Business School who, with his colleague Jan W. Rivkin, has published research on how businesses can use analogic reasoning as a strategic tool. Human beings are analogy machines, he notes, dealing with new information by comparing it to things they already know something about.
That's true, I often try out analogies when I'm trying to understand or explain something. And I can really see how that could lead to innovations, as well as to some odd product evolutions. For a consumer example, I love how the iPhone lets me listen to my voicemail messages in any order, instead of sequentially, which must have been a leftover paradigm from when messages were stored on an analog tape. I can picture someone saying - "why can't I access my messages like I read my email?" - and voila - innovation.
Then I started wondering just how much you could tinker with the crash replay. Could you start eliminating concurrently-running applications, for example, to see if any of them contributed to the crash? And could you test a fix with the replay to see if it fixes the crash?
I also wonder whether IBM's customers would voluntarily seek out software like this to help them narrow down problems. It's not from IBM, and I really don't know any more about it than is in the article above. It's from a company called Replay Solutions, and it runs on several versions of the Microsoft Windows operating system. So, no mainframe support yet (grin). But you could ask them about it!
I heard an interesting story on the news last week, about how the individual states of the U.S. were graded on how they use information. The state I live in, California, got a C+. How can this be, with our advanced technologycenters in Silicon Vallley?
I found the article online here and found some interesting things, although nothing specific about California.
The article says:
Well, that sounds a lot like stuff that I have talked about when describing IBM's Information on Demand strategy. Is your organization good at doing this? I particularly noted the last point in the article, because some of the states complain that their legislators just aren't interested in using the data! Maybe we information professionals have to make that easy (and fun?) to do.
What about the highest-graded states? The article had this to say about one of them:
Yep... this is what everyone wants to know. What did we say we'd do? Did it make a difference? In fact, I've been trying to get this type of information from my financial analyst for some time!
What about states that were graded worse than California?
OK, well, perhaps that is an example of too much information! :-)[Read More]
Announced today: New pricing options for DB2 for z/OS running new workloads! All you data center folks who lament to us that pricing for "other" databases can't be compared to DB2 for z/OS - rejoice!!
Announcing today, and already found here is this gem of a news item tidbit:
IBM is also announcing the immediate availability of DB2 for z/OS Value Unit Edition, which provides a new one-time-charge offering that enables the deployment of new application workloads. This offering strengthens the role of System z as a cornerstone for key business initiatives such as SOA, Data Warehousing, Business Intelligence and packaged applications such as SAP. DB2 for z/OS Value Unit Edition and IBM Information Server enable System z clients to further deliver trusted information for their dynamic warehousing requirements.
Just updated: Here is where you can find the gory details.
Is this cool or what? Doesn't this just remove the last and final objection that the application architects have for leaving DB2 for z/OS out of the running for those new applications?
Now, lest you think I am somehow reflecting a non-developer perspective, look, I have spent most of my efforts in DB2 for z/OS developing the kinds of new technologies designed to attract new workloads, and since even I have heard the pricing objection, isn't it perfectly fair for me to mention this in my DW space? And heck, since I am a developer, not a pricing person by any stretch of the imagination, if this has gotten my attention, you know it's big news!
Bring on those new workloads! And then come to us in development and tell us what you need to bring more work onto z, OK?
When I describe native SQL procedures in DB2 9 for z/OS, I often hear variations of these types of questions:
In order to answer this, I have to explain a little bit about how DB2 handles native SQL procedures. They are simply packages, with "runtime structures" for the SQL statements to be executed. So, when you invoke a native SQL procedure, DB2 finds and loads the package and executes the statements.
In contrast, an external stored procedure with SQL needs a complete language environment for the user program, and then that external program comes back to DBM1 to get its package loaded and SQL statements executed. That's what needs to be "throttled" - the external program execution environments and their associated TCBs. When an incoming stored procedure request is queued for WLM, the DB2 thread is suspended in DBM1. Many customers have experienced delays and DBM1 storage problems when their WLM goals weren't adjusted properly and the queued requests built up. The solution is to either adjust the WLM goals, or else adjust the limit on DB2 threads (local and/or distributed).
With native SQL procedures, the thread will just switch packages when the call statement is processed and run the procedure - no queuing. The storage used for the local variables is above the bar and managed with efficient algorithms. The maximum concurrent first-level native SQL procedures is effectively the same as your setting for maximum DB2 threads. (What I mean by first-level is that a native SQL procedure may have a nested call to another native SQL procedure, so the actual number of concurrent native SQL procedures may be even higher).
So, I guess the way I'd answer the questions is:
Of course I recommend that you test your native SQL procedures in your environment and measure for yourself, and do capacity planning based on the results of your testing. Native SQL procedures will use some DBM1 storage, after all, and how much depends on what statements and what variables are used in the program.
PeggyZ 060000UWWS Tags:  stored_procedures db2_z/os metadata_stored_procedure... 7 Comments 2,967 Visits
Also among the 'recommended practices' that I often present on DB2 for z/OS stored procedures is this one:
Many invocations of DB2 for z/OS stored procedures come from a Java(TM) or a CLI application. The software stack for these programs accessing DB2 for z/OS is through a "driver" program. These driver programs have SQL packages bound to DB2 for z/OS, and in the case of the application invoking a stored procedure, there is a fair amount of code executed in the driver program.
For a CLI program (the term CLI is often used interchangeably with ODBC) -- this is usually something running from a Microsoft(TM) application accessing DB2 for z/OS. The DB2 connect software that includes the driver for DB2 for z/OS has some smarts in it so that if the application is coded using incorrect data types for the stored procedure being invoked, the driver recovers and invokes the SQLPROCEDURECOLS metadata stored procedure on DB2 for z/OS to find out what the data types are and then re-sends the stored procedure call to DB2 for z/OS. Yes, you got it right, this means that a poorly coded application can invoke 3 stored procedure calls for every SQL CALL it's trying to do -- one to the original SP, one to SYSIBM.SQLPROCEDURECOLS, and then again to the original SP with the correct parm types! How do you recognize this? Well, you could run a client-side DRDA trace and it will show up there. Or you can look at statistics at the server. Or you can set the value DESCRIBEPARAM=0 in the db2cli.ini file on the client, and let the applications get the error SQLCODE -301 because now the driver won't do the metadata PS call and instead will let the application fail due to using the wrong datatype. Same result if you issue a -STOP PROCEDURE (SYSIBM.SQLPROCEDURECOLS) ACTION(REJECT) command on the DB2 for z/OS server.
For a Java(TM) program, the current driver is the DB2 Universal Java Driver, and it will not invoke the metadata stored procedure. So this is an excellent reason to switch to the current driver, because the older version of the driver went through the CLI code path and had the same problem as described above.
Note that if you invoke a stored procedure from the command line (the CLP), that code will always invoke the SQLPROCDURECOLS stored procedure since the command line doesn't provide anything for what data type the arguments are.
Now, if you are stuck with a CLI program that you can't modify, what can you do to improve the performance of SQLPROCEDURECOLS? Well, APAR PK57017 just shipped which reduces the size of the package for this stored procedure, so you can free up some EDM pool usage and get a small CPU usage improvement. You can also be sure you run RUNSTATS so that the data access for this SP is the most efficient it can be. I have also heard rumors of some customers creating additional indexes on the tables used by SQLPROCEDURECOLS, but I don't have any specifics on that, sorry.[Read More]
PeggyZ 060000UWWS Tags:  stored_procedures db2_limits wlm_application_environme... db2_z/os 8 Comments 1,720 Visits
Among the 'recommended practices' that I often present on DB2 for z/OS stored procedures is this one:
Let me explain why I recommend this. It's actually at the bottom of the list, and that's because it doesn't come up that often. But it has, and when it does, it can cost in I/O. DB2 has a Language Environment table of load modules in each stored procedures address space. For stored procedures defined STAY RESIDENT YES, we only have room for 512 load modules in that table. A load module has to be in the table in order for DB2 to invoke it. So, starting with the 512th, we'll delete it from the table after we call it, even if it's STAY RESIDENT YES. And come to think of it, we have separate tables for TYPE MAIN and TYPE SUB.
So to be completely accurate, the recommendation could actually say something like this:
For that last bit, remember that different invokers of a stored procedure that end up classified in different WLM enclaves will not have their SPs run in the same instance of a WLM-SPAS.
What's a WLM-SPAS? It's what I use to abbreviate a "WLM-established stored procedures address space".
And this post has motivated me to get a more recent copy of my stored procedures recommended practices presentation out online![Read More]
PeggyZ 060000UWWS 934 Visits
I found this article online today, which highlights the importance of enterprise search.
Company networks contain mountains of structured and unstructured data archived in numerous formats, some of them decades old and stored in secure servers.
IBM also is building a portfolio of enterprise search tools and services, under the OmniFind brand.
Of course you know that DB2 for z/OS data contains mountains of information! This is what our just-released text search support addresses for DB2 for z/OS data - character, binary, and XML. And it's built on OmniFind technology. With this support, you can do text search queries using the built-in CONTAINS() function. It's provided with DB2 9 for z/OS and the no-charge accessories suite.
Now, I know that this is just one piece of enterprise search. In fact, I joke with my colleagues that all of the work that we've put into this is "just an SQL statement". :-) But hey, it's an important piece - it can keep the DB2 for z/OS data where it is and "let the searches come to us".[Read More]
We made a change in DB2 9 for z/OS in order to better package java(TM)code. We now ship DB2 java code such as that required for our XML schema registration and text search password encyrption, to be installed in an HFS/ZFS directory like /usr/lpp/db2/db2910_base
If your installation lets SMP/E default to that directory, then the same set up you use for Java stored procedures in DB2 for z/OS V8 will continue to work. But if you change that, then you need to set a new ENVAR in your JAVAENV dataset such as "DB2_BASE=/usr/lpp/db9a/db2910_base" so we can find our code. Otherwise, you'll see this error when the WLM-SPAS tries to start up: java.lang.NoClassDefFoundError: com.ibm.db2.dsnx9.JARLoader
I know, there are an awful lot of "moving parts" to setting up for running java stored routines. You need the DB2 universal java driver, the z/OS JVM, and JCL and a JAVAENV dataset. The stored procedures redbook has a good chapter on setup. It's a complex environment, but a very powerful one, too![Read More]
We now have the capability in DB2 9 for z/OS to search text data that is stored in DB2 for z/OS using SQL statements. Wahoo!
You mean you missed the announcement?
And you just followed that link and still couldn't find it? It's under "utilities", no, it's not that kind of utility, but still, that's where it is.
What is added is built-in functions for contains() and score(), and also shipping a text search server which runs on a separate, non-z/OS server. For more details, see the announcements!
One prerequisite for this is to have a WLM application environment set up to run a java user-defined function. The early customers I've been working with have had the most stumbling with this part of it. So, this is something you can set up even if you are not quite to DB2 9 for z/OS yet. I'll post some more on the setup steps for that.
So, what kind of data are you going to search, and what kinds of searches are you going to do?[Read More]