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Teradata Interview Questions

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Fload, mload and error tables

Asked By: rakesh5300 | Asked On: Feb 8th, 2008

How many error tables are there in fload and what are their significance/use?Can we see the data of error tables?How many error tables are their in mload and what is there use?When mload job fails, can we access mload tables? If yes then how?

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Answered by: SHUBH25

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Member Since Feb-2008 | Answered On : Feb 15th, 2008

Fload uses 2 error tables

Error table 1: where format of data is not correct.

Error table 2: violations of UPI

Mload also uses 2 error tables (ET and UV), 1 work table and 1 log table

1. ET TABLE - Data error

MultiLoad uses the ET table, also called the Acquisition Phase error table, to store data errors found during the acquisition phase of a MultiLoad import task.

2. UV TABLE - UPI violations

MultiLoad uses the UV table, also called the Application Phase error table, to store data errors found during the application phase of a MultiLoad import or delete task

3. WORK TABLE - WT

Mload loads the selected records in the work table

4. LOG TABLE

A log table maintains record of all checkpoints related to the load job, it is essential/madatory to specify a log table in mload job. This table will be useful in case you have a job abort or restart due to any reason.

Shubhangi

Answered by: prasadh on: Oct 10th, 2014

In fload and multi load we have 2 error tables for a target table, if script run successfully with return code 0 we can see the error tables data(no errors tables will dropped).
tables are locked if script fails we can't see them its under loading....

Answered by: Umar on: Oct 8th, 2013

My question is what if fastload fails, how can we access fastload error table ??? Quick response would be appreciated.

What are two examples of an oltp environment?

Asked By: Interview Candidate | Asked On: Jun 15th, 2005

Ť† transactions take a matter of seconds or less.Ť† many transactions involve a small amount of data.

Answered by: rishabh gupta on: Sep 26th, 2014

Basically OLTP is used for normalized for efficient search & update to prevent redundancy

Answered by: Abhilash AS on: Jan 11th, 2011

Best example is ATM Transactions...

How does indexing improve query performance?

Asked By: Rahul Deshmukh | Asked On: Aug 27th, 2006

Answered by: d on: Jun 25th, 2014

High Confidence: The stats are collected

Low Confidence : Stats are not collected but the used the index columns in where condition and join conditions

No Confidence : No stats and not used the index columns in where and join conditions

Answered by: Sangra on: Feb 7th, 2010

Indexes in Teradata are bit different than Oracle. Primary Index(PI) in Teradata is solely related to the data distribution i.e. decide how evenly the data can be distributed across all AMPs. Primary ...

What is the difference between GLobal temporary tables and volatile temporary tables?

Asked By: Shilpa.bateja | Asked On: Sep 24th, 2007

GLobal temporary tables (gtt) -1. When they are created, its definition goes into data dictionary.2. When materialized data goes in temp space.3. Thats why, data is active upto the session ends, and definition will remain there upto its not dropped using drop table statement.If dropped from some other...

Answered by: Bikhayat kumar on: Feb 10th, 2014

GTT takes up space from temporary space where as VTT takes up space from spool. GTT survive TD system restarts where as VTT does not. GTT allows index to be created where as VTT does not. In a sing...

Answered by: Prashant Nile on: Dec 13th, 2013

GTT uses the Temp Space where as Volatile table use the Spool Space. Both are Session Based once you logged of Data gets vanished. For GTT Definitions remains as it is, as it gets stored in Data Di...

Teradata performance tuning and optimization

Asked By: dheeraj reddy chala | Asked On: Feb 4th, 2008

What is an optimization and performance tuning and how does it really work in practical projects. Can I get any example to better understand.

Answered by: tdguy on: May 22nd, 2013

Performance tuning:
1. Look at the plan generated by PE.
2. Check for the recommendations of stats to be collected for the columns.
3. Try to avoid product joins and unnecessary joins.
4. Try to avoid casting in join conditions
5. Use secondary index appropriately.
6. Use join index if necessary.

Answered by: debashish.munshi on: Sep 18th, 2012

Optimization of queries improves performance of TD and helps the PE to generate the most efficient execution plan. To Optimize a query, choose the Primary Index to avoid skrew, Collect statistics on t...

Join stratagies

Asked By: satishlive | Asked On: Nov 22nd, 2008

There are 2 tables, table a with 10 million records, table b has 100 million records, now we are joining both tables, when we seen explain plan the plan showing td will took the table a and it will redistributes itnow the question is: by that plan is the optimizer is correct job or not ? Justify ans2....

Answered by: yuvaevergreen on: May 22nd, 2013

Merge join strategies are 1. Big and small table joins - duplicate small tables 2. Column used in join is PI for one table - redistribute the other table in spool. 3. Column used in join is non PI f...

Answered by: on: Sep 18th, 2012

There are 2 tables, table A with 10 million records, table B has 100 million records, now we are joining both tables, when we seen Explain Plan the plan showing TD will took the table A and it will re...

Vertical & horizontal partitioning, join & hash indexes and ppi?

Asked By: Sangra | Asked On: Feb 22nd, 2010

What are the differences between the followings?- vertical & horizontal partitioningvs- join & hash indexes vs- ppi

Answered by: yuvaevergreen on: May 20th, 2013

Horizontal partitioning is used in large tables where no of rows are very high. Rows are broken and placed in partitions. Loading becomes faster and query performance would be good. Vertical partitio...

Answered by: sureshkuncham on: Nov 16th, 2012

PPI does not support any join index and hash index

What are the enhanced features in teradata v2r5 and v2r6?

Asked By: RAVI | Asked On: Aug 21st, 2007

Answered by: shams756 on: Nov 2nd, 2012

V2R6 FEATURES
1. Queue Tables are added.
2. Triggered Stored Procedure added.
3. Stored Procedure Grammar Merge added.
4. Multi statements request submitted (supported in stored
procedures by using
BEGIN REQUEST
------
END RESQUEST.

Answered by: navneet_iway on: Jun 11th, 2008

V2R6 included the feature of replica in it.in which copy of data base are available on another system.meam V2R6 provide the additional data protaction as comprison to V2R5 while if data from one system has been vanishes.

What is basic teradata query language?

Asked By: radhashyam_k | Asked On: Apr 5th, 2007

Answered by: debashish.munshi on: Sep 18th, 2012

Basic Teradata Query Language or Batch Teradata Query Language is one of the effective utility in teradata. As using BTEQ we can write SQL statements in Interactive as well as Batch modes. using Bteq you can also Import Export data. Although for Importing and Exporting you have other utilities.

Answered by: krishna on: Jul 30th, 2012

Hello readers
it is just like sql assistance, but giving better performance then sql assistance, bteq work in from host (cli) where as sql runs from odbc so it having lot more opses (gateway) so gives some what less then bteq.

What is fsldm in teradata ?

Asked By: srisree | Asked On: May 17th, 2012

Answered by: Vijaylaxmi on: May 31st, 2012

FSLDM - Financial Services Logical Data Model (Teradata FS-LDM 7.0) its developed by Teradata for the financial sectors (Specifically for Bank). it can be customized based on the user requirement.

Skewness

Asked By: kamalkumarms | Asked On: Oct 25th, 2010

What is the meaning of skewness in teradata? When do we use nullif function in teradata?

Answered by: msrakesh on: Mar 29th, 2012

When we choose wrong primary index the data unevenly distributed across all the amps means some amps have more records and some amps had less records this is called skewness.
Percentage of skewness is called skew factor.30% skew factor is acceptable.

Answered by: Ajay Sai Veerapaneni on: Oct 27th, 2010

Skewness is the statistical term, which refers to the row distribution on AMPs. If the data is highly skewed, it means some AMPs are having more rows and some very less i.e. data is not properly/evenl...

Teradata versions

Asked By: ashlesha143 | Asked On: Oct 27th, 2011

How many version is there in teradata? Please give me detail information for version ? Version name and particular date ?

Answered by: sunil on: Mar 24th, 2012

The following are Teradata Versions as I known.

1. Teradata v2r5
2. Teradata v2r6
3. Teradata 12
4. Teradata 13
5. Teradata 13.10
6. Teradata 14

Now Teradata 14 is the latest one, Teradata 14.10 is upcoming release


Which two statements are true about a foreign key?

Asked By: Interview Candidate | Asked On: Aug 3rd, 2005

Each foreign key must exist as a primary key.Foreign keys can change values over time.

Answered by: thirupathi on: Jan 5th, 2012

The utilities are in teradata as follows

Bteq for loadind/Unloading the data

Fload for load the data only one table at a time it must be empty

mload for load the data which is empty or populated table up to 5 tables at a time

fexport to export the data

tpump to load the data upto 64 tables

Answered by: shahid on: Nov 21st, 2011

Both statements are TRUE

How many codd's rules are satisfied by teradata database?

Asked By: vanshika | Asked On: Nov 21st, 2006

Answered by: Ankal on: Oct 14th, 2011

11 1/2 or 12 codd's rules support

Answered by: Naveen Reddy on: Aug 11th, 2011

12 rules only

What is explain in teradata?

Asked By: dheeraj reddy chala | Asked On: Feb 4th, 2008

What is explain and how does it work?

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Answered by: Madhulathamadduri

View all questions by Madhulathamadduri   View all answers by Madhulathamadduri

Member Since Jan-2010 | Answered On : Apr 15th, 2011

The EXPLAIN modifier preceding an SQL statement generates an
English translation of the optimizer’s plan. It is fully parsed and
optimized, but not executed.
EXPLAIN returns:
Text showing how a statement will be processed (a plan).
An estimate of how many rows will be involved.
A relative cost of the request (in units of time).
This information is useful for:
• Predicting row counts.
• Predicting performance.
• Testing queries before production.
• Analyzing various approaches to a problem.
EXPLAIN may also be accessed using Teradata Visual Explain.

Answered by: senthang on: Jun 22nd, 2011

1. English version on optimizer plan2. to identify the objects used and kind of locks applied on those objects3. to identify the number of amp operation eg. single ot group amp4. to identify the data ...

Answered by: yuvaevergreen on: Jun 6th, 2011

Explain statement generally gives the step by step analysis of the queries being executed in the database. It is the plan prepared by PE dispatched to the amps. It could also identify intermediate sp...

Multiset table and duplication

Asked By: Madhu Priya | Asked On: May 14th, 2010

Why fastload does not support multiset table and duplication?

Answered by: senthang on: Jun 22nd, 2011

Fastload will support the MULTISET table but it will ignore the all row duplicates because of the restartability mechanism of fastload.

Answered by: yuvaevergreen on: Aug 13th, 2010

Fastload utility does not support duplicate rows. 1.Since MS table supports dup rows, fastload cannot load MS table.2.Restart logic is one of the reason. Fastload is one of the utility which load...

What is the purpose of before journal and after journal?

Asked By: menakamahalingam | Asked On: Mar 22nd, 2011

Answered by: yuvaevergreen on: Jun 7th, 2011

Before Journal keeps the images of the table before making the change to the table. Very useful, if the changes need to be reverted incase of a fault or rollback. After Journal keeps the images of the table after the changes has been made to the table. 

Answered by: SanthuTeradata on: Mar 29th, 2011

We use both before journal and after journal in Permenent journal to do selective or full recovery of data..........consider Today Monday**Yesterday--------->Before ImageTuesday------------>Afte...

What is cliques? What is vdisk and how it will communicate with physical data storage at the time of data retrieval through amp ?

Asked By: chinmoy.chaudhuri | Asked On: May 7th, 2007

Answered by: rajnsuccess on: Feb 6th, 2011

Clique is mainly used to prevent node failures.Group of nodes which share common disk drives is called CLIQUE.Group of cylindrical or physical disks arranged in array fashion is called VDISKS.After AM...

Answered by: Sangra on: Feb 22nd, 2010

In case of one Disk failure the mirrored disk would provide the fallback protection In case of AMP failure the second AMP (in the fallback Clique) can provide the protection In case of Node failure th...

Skewness

Asked By: muralidharr | Asked On: Jan 19th, 2011

How will you avoid skewness?

Answered by: debojitpal on: Feb 1st, 2011

Data or Amp skew occurs in teradata due to uneven distribution of data accross all the amps. Often, this leads to spool space error too. To avoid skewness, try to select a Primary Index which has as m...

What is a common data source for the central enterprise data warehouse?

Asked By: Interview Candidate | Asked On: Jun 15th, 2005

Operational data stores

Answered by: Abhilash AS on: Jan 11th, 2011

ODS (Operational Data sources) or Datamarts

Answered by: sithusithu on: Jan 30th, 2006

ODS=>Operational Data SourceCheers,Sithu

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