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Log Table
What is log table? What is the use of log table?
saiteja
- Jun 29th, 2017
Log table maintain records of all checkpoints log table is used for restartability
yuvaevergreen
- Oct 7th, 2010
Log table in MLOAD is used to store the results of each phase of the operation. This log table is used by MLOAD for restarting the mload process from the appropriate checkpoint i.e. after the successful phase.
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MultiSet Table and Duplication
Why fastload does not support multiset table and duplication?
saiteja
- Jun 16th, 2017
Fastload does not support duplicates because storing duplicates in fastload is difficult to the system decreases the performance of the fastload when the fastload script fails when you restart the fastload script and the same row hash value is loaded in to second time
senthang
- Jun 22nd, 2011
Fastload will support the MULTISET table but it will ignore the all row duplicates because of the restartability mechanism of fastload.
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Fload, Mload and error tables
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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SHUBH25- Member Since Feb-2008 | 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 errorMultiLoad 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.
ShubhangiCHetan
- Jun 9th, 2017
There are 2 error tables in Fastload, Error table 1 significance is to capture datawhich do not match the speciied datatype, and Error table 2 is for the Uniqueness constraint.. In case you have UPI d...
prasadh
- 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.... -
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Skewness
What is the meaning of skewness in Teradata? When do we use nullif function in Teradata?
arunFERGY
- May 31st, 2017
Unequal distribution of data on amps is called skewness. Nullif function compares two arguments, if they matches then it returns null else it returns first argument.
msrakesh
- 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. -
Skewness
How will you avoid Skewness?
arunFERGY
- May 25th, 2017
Unequal distribution of data on amps is called skewness. Choose PI columns as unique as possible to avoid this.
debojitpal
- 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...
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What are two examples of an OLTP environment?
è Transactions take a matter of seconds or less.è Many transactions involve a small amount of data.
rishabh gupta
- Sep 26th, 2014
Basically OLTP is used for normalized for efficient search & update to prevent redundancy.
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What is the difference between Global temporary tables and Volatile temporary tables?
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 session then its should be Drop table all;4. you can collect stats on GTT.Volatile Temporary tables...
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Teradata performance tuning and optimization
What is an optimization and performance tuning and how does it really work in practical projects. can i get any example to better understand.
tdguy
- 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.debashish.munshi
- 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...
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Join Stratagies
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. From the same above example now the optimizer is taking Table B (100 million records) and it is distributing...
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Vertical & Horizontal Partitioning, Join & Hash Indexes and PPI?
What are the differences between the followings?- Vertical & Horizontal Partitioningvs- Join & Hash Indexes vs- PPI
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What are the enhanced features in Teradata V2R5 and V2R6?
shams756
- 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
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END RESQUEST.
navneet_iway
- 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.
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What is basic teradata query language?
debashish.munshi
- 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.
krishna
- 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. -
Teradata versions
How many version is there in Teradata? please give me detail information for version ? Version Name and Particular date ?
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Which two statements are true about a foreign key?
Each Foreign Key must exist as a Primary Key.Foreign Keys can change values over time.
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What is explain in teradata?
What is explain and how does it work?
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Madhulathamadduri- Member Since Jan-2010 | 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.senthang
- 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 ...
yuvaevergreen
- 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...
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What is the purpose of Before Journal and After journal?
yuvaevergreen
- 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.
SanthuTeradata
- Mar 30th, 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...
Teradata Interview Questions
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