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Welcome to Datavail’s Blog, where you can read the latest insights, tips and opinions of our experts on all things data and technology.

Author: Craig Mullins
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How and When to Use DB2 Scrollable Cursors

If you are using DB2 V7 or higher, consider using scrollable cursors. With scrollable cursors, you can move directly to the rows you want without having to FETCH every other row returned by the cursor.

Craig Mullins | May 19, 2015

Using Nulls in DB2

A null represents missing or unknown information at the column level. If a column “value” can be null, it can mean one of two things: the attribute is not applicable for certain occurrences of the entity, or the attribute applies to all entity occurrences, but the information may not always be known.

Craig Mullins | April 6, 2015


DSNTEP2 is an application program that can be used to issue DB2 dynamic SQL statements. It is sometimes referred to as “Batch SPUFI” because it allows you to submit SQL in batch similar to how SPUFI allows online SQL execution. The following sample JCL demonstrates the capability of DSNTEP2 to issue DCL, DDL, and DML dynamically.

Craig Mullins | February 19, 2015

VSAM Demystified

VSAM is used “under the covers” of every DB2 for z/OS page set. VSAM is also used as the storage mechanism by some IMS databases. It is also used to store a lot of mainframe data outside the control of any DBMS. But there is a lot of confusion about what exactly VSAM is, how it can be used, and how it differs from a DBMS.

Craig Mullins | February 2, 2015

Minimizing Lock Contention Issues

I frequently get e-mails with DB2 questions and I plan to start posting answers to some of the more common ones up here. One issue that comes up a lot is dealing with locking issues. Usually it is posed by someone who is experiencing timeouts in an online environment and they want to know how to minimize them. Here is some guidance.

Craig Mullins | December 30, 2014

No Black Boxes!

I’ve written about this subject before, but I think it is important enough to merit another go-round. First of all, before I go any further, let’s first define what I mean by a “black box.” If I plan to recommend that you prohibit them we better both understand what it is we are talking about proscribing.

Craig Mullins | December 23, 2014

DB2 Compression: z/OS versus LUW

Data compression for non-mainframe DB2 is quite a bit different than it is for DB2 for z/OS. In mainframe DB2, specifying COMPRESS YES on the CREATE TABLESPACE statement will cause DB2 to implement Ziv-Lempel compression for the table space in question. Data is compressed upon entry to the database and decompressed when it is read.

Craig Mullins | December 16, 2014

The Aging Mainframer

A continuing, lingering perception that the mainframe is dead continues on in some parts of the IT industry. It seems that we constantly hear that big IT shops are getting rid of their mainframes. But rarely do we ever hear about it after the fact. No, it is usually reported right when someone thinks that it is a good idea.

Craig Mullins | December 4, 2014

Webinar: Building a Performance Centric Organization

Database performance problems are not caused by magic. Indeed, all performance problems are always caused by change. That statement flies in the face of what I normally say, which is “Almost never say always or never”… but in this case, it is true.

Craig Mullins | November 11, 2013
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