Tuesday, April 14, 2020

Db2 for z/OS and Managing Database Changes - Part 1

Today we begin a multi-part series of blog posts taking a look at what is involved in making database changes in a Db2 for z/OS environment. The first thing that DBAs will need is the ability to change all the database objects supported by Db2 for z/OS. There are numerous different types of  database objects and structures that can be created and modified by DDL, and at one point or another, DBAs are called upon to create, alter, and drop every one of them.
But let’s dig a little deeper into what is required. Assume that you are a Db2 DBA who has been given a request to make several changes to database structures. The first thing you must do, of course, is to review the requested changes to make sure they are appropriate. Assuming they are, what is the next step?

You must determine how to go about making each change. At a high level, there are three different types of schema changes: 
  • simple (or immediate), 
  • medium (or pending), and 
  • complex. 

Simple changes can be implemented immediately without requiring intervening actions. Medium changes require a bit more work to implement by running a REORG, and then we have complex changes that require an in-depth script for dropping and re-creating the database object. But not every type of database change request can use each type of schema change method. There are requirements and nuances in deciding which method can be used when.

In our next blog post, we will discuss simple Db2 changes.

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