One area that tends to confuse some DB2 developers until they gain experience is how DB2 partitioning works. A common question I get goes something like this: “If a table is in a partitioned table space, say four partitions, for example, then to process the table in batch can I run four instances of the batch program in parallel, one against each partition. What do I code to do this?”Well, the short and sweet answer to this question is “Yes, you can run four instances of a batch program in parallel if you so desire.” But there is a nuance to this...
Thursday, 31 August 2006
Tuesday, 29 August 2006
How are Indexes Being Used?
Posted on 12:31 by Unknown
In keeping with my promise to periodically post blog entries based on questions I have received, here we have another question I have been asked:If I have five indexes on a table, what is the best way to determine if all, some or none of the indexes are being used?Here is the answer I sent:The best approach would be to make sure you have run EXPLAIN on all of your production plans and packages. Then examine the PLAN_TABLE output for those indexes. For example:SELECT *FROM my.PLAN_TABLEWHERE ACCESSNAME IN (put your list of indexes here); Of course,...
Thursday, 24 August 2006
VARCHAR versus Compression
Posted on 10:55 by Unknown
A couple of days ago I posted a blurb giving advice on using variable character columns in DB2. After thinking about the topic a little bit more, I decided to post a follow-on topic: namely, comparing the use of VARCHAR to DB2 compression.Even though these are two entirely different "things," they are each probably done for similar reasons - to save disk storage. VARCHAR does this by adjusting the size of the column to fit the actual length of text being stored; compression does this by sending rows of data through an algorithm to minimize its...
Monday, 21 August 2006
IBM Mainframes - Not Just for Big Shops Any More
Posted on 12:42 by Unknown
Just a quick blog today to point you to an interesting article in the latest issue of IBM Systems Magazine - Mainframe Edition. The article, titled A New System for a New Market, points out that the System z9 Business Class (z9 BC) platform, the latest mainframe in IBM's product line announced in April 2006, is suitable for the small and medium business (SMB) space.This offering brings high performance and scalability to the SMB market at a very reasonable cost (around $100k). With specialty engines that can be added (IFL, zIIP and zAAP), again...
Sunday, 20 August 2006
Advice on Using Variable Character Columns in DB2
Posted on 21:36 by Unknown
One of the long-standing, troubling questions in DB2-land is when to use VARCHAR versus CHAR. The high-level advice for when to use VARCHAR instead of CHAR is for larger columns whose length varies considerably from row-to-row. Basically, VARCHAR should be used to save space in the database when your values are truly variable.In other words, if you have a 10-byte column, it is probably not a good idea to make it variable... unless, of course, 90% of the values are only one or two bytes, then it might make some sense. Have you gotten the idea here...
Thursday, 17 August 2006
Greatest Software Ever?
Posted on 14:05 by Unknown
I just stumbled across a very interesting article this afternoon and thought I'd share it with everybody through my blog. The article, published in Information Week is titled What's The Greatest Software Ever Written? And isn't that an intriguing question?Well, I read through the article and other than a few quibbles here and there I'd have to say that the author did a good job of assembling his list. He spends quite a bit of time talking about the IBM 360 project - and well he should. This was one of the first truly huge software projects and...
Thursday, 10 August 2006
SHARE Travelers Take Heed
Posted on 09:17 by Unknown
With the upcoming SHARE conference in Baltimore next week, there are sure to be many of you out there who will be traveling to the nation's capital region over the weekend. As you prepare to travel, be sure to factor in additional time at the airport due to the latest TSA warning.Basically, in response to a recently thwarted terrorist plot in the UK, the threat level has been raised to High (or Orange) for all commercial aviation operating in or destined for the United States. That means the lines will be longer and the searches more thorough...
Wednesday, 9 August 2006
Where exactly is a DB2 plan stored?
Posted on 12:21 by Unknown
The title of this posting is a question I received awhile ago. As I promised earlier on this blog, I will periodically post the answers I have given to e-mailed questions. So, here goes:A DB2 "plan" is stored in the DB2 Directory and information about the plan is stored in the DB2 Catalog.The DB2 Directory table that contains actual plans is SYSIBM.SCT02 (and SYSIBM.SPT01 contains actual packages). The plan is stored as an internal structure called a cursor table; packages are stored as package tables. As DB2 runs application programs, it loads...
Tuesday, 8 August 2006
Mainframe Weekly: A new mainframe-focused blog
Posted on 13:41 by Unknown
Mainframe Weekly is a new blog featuring the insights of Trevor Eddolls. Trevor is an editor who has worked for Xephon for some time. Xephon publishes those "Update" journals - you know the ones, DB2 Update, CICS Update, etc. The ones that are full of content and don't accept any ads.I've had the pleasure of writing for DB2 Update and working with Trevor for a number of years now, and I look forward to regularly reading his new blog. Recent entries there have covered CICS, DB2 and Viper, and storage technology.Do yourself a favor and be sure to...
Monday, 7 August 2006
Upcoming SHARE Conference
Posted on 08:14 by Unknown
Just a quick posting to remind everyone that the bi-annual SHARE conference is coming up next week in Baltimore, MD. For those of you who don't know about SHARE: the conference has offered education to IT professionals, improving the value of IT to businesses, and advancing careers since 1955 - the longest history of any IT user group.SHARE in Baltimore runs from August 13-18, 2006 and, as usual, there will be a plethora of useful and educational sessions on multiple IT topics. According to the folks at SHARE there will be over 800 technical sessions...
Wednesday, 2 August 2006
New Mainframe Redbook
Posted on 13:47 by Unknown
IBM published a new mainframe redbook this week that everyone who works with mainframe technology should download and have handy. It is titled Introduction to the New Mainframe: z/OS Basics and it offers a very nice high-level overview of mainframe technology circa 2006.Of course, if you are a long-time mainframer much of this redbook may be too high level for you. But it will be just the right thing to have at your disposal when someone drops by to ask a basic question. Just e-mail them a copy of the book.And even long-time experts still might...
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