Db2 12 for z/OS Function Level 509

Late last month, February 2021, IBM introduced a new function level, FL509, for Db2 12 for z/OS. You can find in-depth details here.

But if you are looking for a high-level synopsis, read on! 

There are several interesting new capabilities introduced with this function level, but perhaps the most important thing that organizations want to know is that there are no new incompatible changes or deprecations introduced with FL509.

Okay, so what’s new here. The first thing to report is an improvement to data security with tamper-proof audit policies. This means that an audit policy cannot be changed, or even stopped, unless requested by an authorized user. And the authorization must be via a z/OS security product (such as IBM’s RACF), not Db2.

This capability provides another step in the separation of duties required for proper auditing. In other words, the audited must not be the controller of the audit policy or auditing capabilities. It also protects administrative users from mistakenly modifying audit policies.

The next new capability delivered by FL509 is high-availability accelerator-only tables. Accelerator-only tables (AOTs) are those defined to the IBM Db2 Analytics Accelerator only, and not in the base Db2 for z/OS. Queries and DML statements issued against AOTs are always routed to an accelerator (because the data does not exist anywhere else).

So, what are high availability AOTs? Well, FL509 delivers the capability to define an accelerator-only table in more than one accelerator. This can improve availability and with workload balancing a query can be rerouted to another available accelerator if the target accelerator is not available.

Also as of FL509, you can specify a compression algorithm at the table, table space, or partition level. This means you can explicitly use either the fixed-length or Huffman compression algorithm at the table, table space, or partition level using CREATE TABLE and ALTER statements. The Db2 catalog is updated to indicate the compression algorithm used for each object.

Finally, FL509 delivers enhanced temporal RI. What this means is that restrictions on UPDATE and DELETE statements are removed relating to the temporal RI introduced originally in Db2 12.

To elaborate, one FL509 is active, when an UPDATE statement with a FOR PORTION OF clause attempts to update the parent table in a temporal RI relationship, the update is allowed as long as the rules of temporal RI are not violated. Likewise, when a DELETE statement with a FOR PORTION OF clause attempts to delete from the parent table in a temporal RI relationship, the deletion is allowed, as long as the rules of temporal RI are not violated.

At any lower application compatibility level, such UPDATE or DELETE statements for a parent table in an RI relationship will fail (with SQLCODE -4736).

Summary

Now that IBM is using function levels to deliver significant new capabilities for Db2 12 for z/OS, it is imperative that your organization keeps up-to-date on this new functionality and determines where and when it makes sense to introduce it into your Db2 databases and applications.

Also, be aware that if you are not currently running at FL508, moving to FL509 activates all earlier function levels. You can find a list of all the current function levels here.