This week I am going to switch gears over to the big iron and talk about DB2 z/OS. IBM has been making great strides in the area of schema management. As any mainframe DBA knows, the process of having to make a seemingly simple schema change can result in a very complex combination of DDL, Utilities and batch processes. These changes can result in applications having to be unavailable for significant amounts of time. Starting with V8 of DB2, IBM introduced the concept of “Online Schema Evolution.” This is the process of being able to make changes to your DB2 objects with very little or no down time by eliminating the need to unload data, drop/recreate objects with dependencies, reload the data and rebind any plans or packages associated with the objects. This is a significant feature when it comes to high availability applications. With the upcoming release of DB2 for z/OS V9 this area continues to evolve.
The first one I want to talk about this week is table cloning. Table cloning is a unique feature that will benefit applications that require high availability such as web based applications. With table cloning you can make an exact copy of an existing table in the same tablespace and then switch back and forth between the tables with almost complete transparency. The cloned table can then be loaded with data just like the original table. This in effect provides a very simple data mirroring facility plus having the ability to have different versions of data.
The other significant schema management features are:
Column renaming – This feature gives you to have the ability to rename table columns without having to drop/recreate the table. This will be a great time saver and potentially eliminate the need to add new columns to a table by allowing for the reuse of existing columns.
Renaming Indexes -This feature can be helpful when maintaining ERP type applications. Many of these applications have the version coded into the name of the indexes. Not having to drop and recreate indexes when a version upgrade is applied will be a huge timesaver.
DB2 has made great strides in improving availability by minimizing the downtime necessary to perform changes to the database structures. This is essential in today’s 24x7 web enabled world. These types of enhancements are ensuring that DB2 z/OS will remain the core data repository for large IT operations for a long time to come.
See you next week!