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4 days ago

The Teradata JDBC Driver Engineering team receives a lot of questions about what happens when a JDBC connection is created. Let's clarify the concepts Laddered Concurrent Connect (LCC) versus COP Discovery versus logon, and review what the Teradata JDBC Driver does to create a JDBC connection.

 

First, some definitions...

"COP" stands for Communications Processor, and is a term originating from Teradata's earliest database appliances in the 1980s. In modern usage, a "COP" is a Teradata Database node that is running a Teradata Database Gateway process.

1 week ago

As of Teradata Database 14.10.05 and 15.00.03, a simplified approach to determining which workload will support session management and parsing has been adopted  This posting describes this more straightforward approach which will be used starting in these 14.10 and 15.0 releases, and going forward in all future releases.

An earlier posting titled:  “A Closer Look at How to Setup a Parsing-Only Workload”  explains how session and parsing workload assignment takes place prior to this more simplified approach.  If you are on an earlier release, please see that posting from December 2014.

1 week ago

There is a demand to have a functionality similar to the industry standard SHA256 hash function to condense RDBMs table content to a single value which is changing completely in case a single bit changes in multi million or billion row tables.

3 weeks ago

The theme of this blog is an examination of forces that would disrupt existing data warehouse implementations.  I categorize these as either long tail or black swan events.

10 Dec 2014

When you think about priorities, you probably focus your attention on AMP work.  Whether you are using Teradata Active System Management (TASM) or Teradata Integrated Workload Management (TIWM), AMP work performed by requests are typically spread across different workloads, with their priorities based on the importance of the work to the business and how long you expect the work to run.

Parsing engine work on behalf of a query runs within a workload as well.  Work performed on the parsing engine is typically very quick and requires very few resources.  So why not run some, or all, of your parsing activity in a very high priority workload where it may be able to complete sooner when your system is busy,  just as you do with your short, critical AMP work?  This posting will explain how parsing priority is determined, and will illustrate the steps involved in increasing parsing priority.

14 Nov 2014

Beginning with Teradata Database 14.0 and Teradata JDBC Driver 13.10.00.21, the Client Attributes feature records a variety of information about the client system and client software in the system tables DBC.SessionTbl and DBC.EventLog.

The Client Attributes are recorded at session logon time. Subsequently, the system views DBC.SessionInfoV and DBC.LogOnOffV can be queried to obtain information about the client system and client software on a per-session basis.

09 Nov 2014

Unstructured data can be dealt with effortlessly in Teradata. Regular expression has been around for many years in software fields. With the advent of Big data, hadoop, NO SQL, columnar, graph database, document  databases the usage of Regex is becoming more and more increasingly popular. The example highlighted below is just a tip of an iceberg of usage. There are umpteen features that can be incorporated into the databases.

02 Oct 2014

The accuracy of sample statistics has been greatly improved over the last Teradata releases. So I usually try to use sample stats on most of the big tables and I found them to be reliable on many columns, not only the officially recommended unique or nearly-unique columns, e.g. on DATEs.

But there is a specific scenario when sample stats result in worst case optimizer plans:

24 Sep 2014

During my first coding class, after the obligatory “Hello, World,” my assignment was to find the least cost path in a matrix of values (linear programming).  The computer took some time to crunch the data to come to a solution.  Now, this is an app on your phone.  

11 Sep 2014

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 software release levels. Some of these recommendations apply to releases earlier than Teradata Database 14.10 and some rely on new features available only in Teradata Database 14.10.

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

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