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Statistical information is vital for the optimizer when it builds query plans. But collecting statistics can involve time and resources. By understanding and combining several different statistics gathering techniques, users of Teradata can find the correct balance between good query plans and the time required to ensure adequate statistical information is always available.

This recently-updated compilation of statistics collection recommendations are intended for sites that are on any of the Teradata Database 14.10, 15.0, or 15.10 software release levels. Some of these recommendations apply to releases earlier than Teradata Database 14.10 and some rely on new features available starting in Teradata Database 14.10.  Statistics collection functionality in the Teradata Database works the same in 14.10, 15.0 and 15.10 releases.

For greater detail on collecting statistics for Teradata Database 14.10, see the orange book titled:  Teradata Database 14.10 Statistics Enhancements by Rama Krishna Korlapati.

Contributors: Carrie Ballinger, Rama Krishna Korlapati, Paul Sinclair, September 11, 2014

How does TASM enforce rules such as classification and workload exceptions against User Defined Functions?  What about table functions and table operators, some of which do their work outside of Teradata?  How far can you rely on TASM classifications using estimated processing time in these cases?  Will there be accurate resource usage numbers reported to support workload exceptions on CPU or I/O?

These are some of the questions that need answering if you are extending the use of simple or more complex user-defined functions on your platform.

Because they look like just another group of workloads, you might think that SLES11 virtual partitions are the same as SLES10 resource partitions.  I’m here to tell you that is not the case.  They have quite different capabilities and purposes.  So don’t fall victim to retro-conventions and old-school habits that might hold you back from the full value of new technology.  Start using SLES11 with fresh eyes and brand new attitudes.  Begin at the virtual partition level.

This content is relevant to EDW platforms only.

If I told you there was a way you might be able to speed up parsing time for your queries, would you be interested?  

In Teradata Database 14.10.02 there is a new capability that allows you to expedite express requests, and I’d like to explain how that works, describe when it can help you, and make some suggestions about how you can use it to get the best performance you can from parsing when the system is under stress.  But first a little background.

The SLES 11 priority scheduler implements priorities and assigns resources to workloads based on a tree structure.   The priority administrator defines workloads in Viewpoint Workload Designer and places the workloads on one of several different available levels in this hierarchy. On some levels the admin assigns an allocation percent to the workloads, on other levels not.

How does the administrator influence who gets what?  How does tier level and the presence of other workloads are on the same tier impact what resources are actually allocated?  What happens when some workloads are idle and others are not?

This posting gives you a simple explanation of how resources are shared in SLES 11 priority scheduler and what happens when one or more workloads are unable to consume what they have been allocated.

An earlier blog post focused on simple steps to get started using the Teradata 14.10 Automated Statistics Management (AutoStats) feature.  One of the new capabilities that AutoStats relies on when it streamlines statistics collection is the new “Threshold” option.  Threshold applies some intelligence about when statistics actually need to be re-collected, allowing the optimizer to skip some recollections.  

Although you will probably want to begin relying on AutoStats when you get to 14.10, you don’t have to be using AutoStats to take advantage of threshold, as the two features are independent from one another.  This post will give you a simple explanation of what the threshold feature is, what default threshold activity you can expect when you get on 14.10, and what the options having to do with threshold do for you.  And you’ll get some suggestions on how you can get acquainted with threshold a step at a time.  

Most Teradata systems support different processing windows, each which has a somewhat different set of business priorities.  From 8 AM to 12 noon the most important work may be the Dashboard application queries.  But from 12 noon to 6 PM it could be the ad hoc business users.   At night maybe it’s the batch loads and reporting.   Planned Environments function within the TASM state matrix to support the ability to automatically manage changes to workload management setup during those different windows of time.

Everyone with a Teradata Database collects statistics.  No way around it.  Good query plans rely on it, and we’ve all gotten used to it.

But starting in Teradata Database 14.10 there’s some big changes.  Numerous enhancements to the optimizer, some important database changes, a new set of APIs, an added data dictionary table, and a brand new Viewpoint portlet all combine together to produce the Automated Statistics (AutoStats) feature.  Used fully, AutoStats can identify statistics the optimizer looked for and found missing, flag unused statistics that you no longer need to collect on, prioritize and execute the stats collection statements, and organize/run your statistics collection jobs in the most efficient way possible.

There’s a lot going on and a lot of choices involved.  So what’s the easiest way to start getting familiar with AutoStats?   And what’s required with the new DBQL logging options?  If you like to build up confidence in a new feature at your own pace, this blog posting offers a few simple steps designed to introduce you to key features and benefits AutoStats.  

I just returned from the 2013 Teradata user group Partners Conference in Dallas.  One of the technical topics that I presented at the conference was throttle rules and how they work.  Throttles provide concurrency control in TASM, both on the EDW and the Appliance platforms.   I'd like to share few points about enhancements to throttles in Teradata 14.0 and 14.10 that I discussed at the conference,  in particular automatic throttles.

Collecting statistics on data dictionary tables is an excellent way to tune long-running queries that access multi-table dictionary views.  Third party tools often access the data dictionary several times, primarily using the X views.  SAS, for example, accesses DBC views including IndicesX and TablesX for metadata discovery.  Without statistics, the optimizer may do a poor job in building plans for these complex views, some of which are composed of over 200 lines of code.

In an earlier blog posting I discussed the value of collecting statistics against data dictionary tables, and provided some suggestions about how you can use DBQL to determine which tables and which columns to include.  Go back and review that posting.  This posting is a more comprehensive list of DBC statistics that is updated to include those recommended with JDBC.