Today we are going to talk about some random DB2 features that can’t stand in a blog of their own, but are worth discussing nonetheless. These are tidbits I had discovered during “DB2’s Got Talent” presentations, IDUG conferences, or “Hey, look what I discovered” moments.
CPUSPEED (Database Management Configuration)
You blow past this setting every time you execute “db2 get dbm cfg”. It’s located at the very top of your output and is one of the more important settings that is overlooked. The result for this parameter is set after DB2 looks at the CPU and determines how fast instructions process through (millisec/instruction).
Optimizer is influenced greatly by this setting. CPUSPEED is automatically set upon instance creation and is often never examined again. The setting will stay static unless you ask DB2 to re-examine the CPU.
So, why do we care? Well there could be a few reasons.
- An additional CPU was added or subtracted from an LPAR.
- An image of your old server was taken and placed on a new, faster server, with a different type or number of processors.
If for some reason your CPU configuration was altered or changed the new processing speed is not taken into account until it is re-evaluated. So go ahead and add on that additional CPU to handle your black Friday workload. It won’t help much unless DB2 knows to take it into account.
db2 "update dbm cfg using CPUSPEED -1"
Once done, you should see a new CPUSPEED displayed for your DBM configuration.
If you are comparing apples to apples you want to see the number get smaller to show a speed increase. If you are changing architecture (P6 to P7 for example) the number could theoretically go up. Put that in context though, the higher number could be the setting DB2 needs to account for multi-threading or some other hardware change. So it may look worse when it really isn’t.
Once done, DB2 will use the new number to determine proper access paths. So make sure to issue a REBIND once done so your SQL can take advantage of the speed increase.
(Special thanks to Robert Goethel who introduced this topic during the DB2 Night Show competition this year).
RESTRICTIVE (Create Database …. RESTRICTIVE)
I picked this up in Roger Sander’s DB2 Crammer Course at IDUG this year. I had just spent the past two months auditing our database authorities and was frustrated with the amount of PUBLIC access. I even created a separate SQL script to run after new database creation to revoke some of the default PUBLIC authority.
Apparently I reinvented the wheel. If you use the RESTRICTIVE clause in the CREATE DATABASE command no privileges or authorities will automatically be granted to PUBLIC.
db2 “create database warehouse on /data1 dbpath on /home/db2inst1 restrictive”
DB2_WORKLOAD (System Environment Variable)
This db2set parameter has been available for a while but I know a new option (ANALYTICS) became available with v10.5. Essentially, DB2_WORKLOAD will preset a group of environment variables for your needs. Set it once and go – no need to look up various configurations or develop scripts. This is valuable for various application configurations such as BLU or Cognos.
db2set DB2_WORKLOAD <option>
|CM||IBM Content Manager|
|COGNOS_CS||Cognos Content Server|
|FILENET_CM||Filenet Content Manager|
|MDM||Master Data Management|
|TPM||Tivoli Provisioning Manager|
|WAS||Websphere Application Server|
If you are a Websphere Commerce nerd like Ember, make sure to read her blog on DB2_Workload and how it can be used for Websphere Commerce.
Michael Krafick is an occasional contributor to db2commerce.com. He has been a production support DBA for over 12 years in data warehousing and highly transactional OLTP environments. He was acknowledged as a top ten session speaker for “10 Minute Triage” at the 2012 IDUG Technical Conference. Michael also has extensive experience in setting up monitoring configurations for DB2 Databases as well as preparing for high availability failover, backup, and recovery. He can be reached at “Michael.Krafick (at) icloud (dot) com”. Linked-in Profile: http://www.linkedin.com/in/michaelkrafick. Twitter: mkrafick
Mike’s blog posts include:
10 Minute Triage: Assessing Problems Quickly (Part I)
10 Minute Triage: Assessing Problems Quickly (Part II)
Now, now you two play nice … DB2 and HACMP failover
Technical Conference – It’s a skill builder, not a trip to Vegas.
Why won’t you just die?! (Cleaning DB2 Process in Memory)
Attack of the Blob: Blobs in a Transaction Processing Environment
Automatic Storage Tablespaces (AST): Compare and Contrast to DMS
DB2 v10.1 Column Masking
Automatic Storage (AST) and DMS
Reloacting the Instance Home Directory
Informational Constraints: Benifits and Drawbacks