informatica faq-13
Q:What are the mapings that we use for slowly changing dimension table?
A:Type1: Rows containing changes to existing dimensions are updated in the target by overwriting the existing dimension. In the Type 1 Dimension mapping, all rows contain
current dimension data.
Use the Type 1 Dimension mapping to update a slowly changing dimension table when you do not need to keep any previous versions of dimensions in the table.
Type 2: The Type 2 Dimension Data mapping inserts both new and changed dimensions into the target. Changes are tracked in the target table by versioning the primary
key and creating a version number for each dimension in the table.
Use the Type 2 Dimension/Version Data mapping to update a slowly changing dimension table when you want to keep a full history of dimension data in the table.
Version numbers and versioned primary keys track the order of changes to each dimension.
Type 3: The Type 3 Dimension mapping filters source rows based on user-defined comparisons and inserts only those found to be new dimensions to the target. Rows
containing changes to existing dimensions are updated in the target. When updating an existing dimension, the Informatica Server saves existing data in different columns
of the same row and replaces the existing data with the updates.
Q:What are the basic needs to join two sources in a source qualifier?
A:Two sources should have primary and Foreign key relation ships.
Two sources should have matching data types.
Q:What is the Default Join that source Qualifier Provides?
A:Inner equi join.
Q:What is the status code?
A:Status code provides error handling for the informatica server during the session.The stored procedure issues a status code that notifies whether or not stored procedure
completed sucessfully.This value can not seen by the user.It only used by the informatica server to determine whether to continue running the session or stop.
Q:Differences between connected and unconnected lookup?
A:Connected lookup:-
1> Receives input values diectly from the pipe line.
2> You can use a dynamic or static cache.
3> Cache includes all lookup columns used in the maping.
4> Support user defined default values.
Unconnected lookup:-
1> Receives input values from the result of a lkp expression in a another transformation.
2> You can use a static cache.
3> Cache includes all lookup out put ports in the lookup condition and the lookup/return port.
4> Does not support user defiend default values.
Q:Why use the lookup transformation?
A:To perform the following tasks:-
Get a related value. For example, if your source table includes employee ID, but you want to include the employee name in your target table to make your summary data
easier to read.
Perform a calculation. Many normalized tables include values used in a calculation, such as gross sales per invoice or sales tax, but not the calculated value (such as net
sales).
Update slowly changing dimension tables. You can use a Lookup transformation to determine whether records already exist in the target.
Q:In which condtions we can not use joiner transformation(Limitaions of joiner transformation)?
A:Both pipelines begin with the same original data source.
Both input pipelines originate from the same Source Qualifier transformation.
Both input pipelines originate from the same Normalizer transformation.
Both input pipelines originate from the same Joiner transformation.
Either input pipelines contains an Update Strategy transformation.
Either input pipelines contains a connected or unconnected Sequence Generator transformation.
Q:What are the diffrence between joiner transformation and source qualifier transformation?
A:You can join hetrogenious data sources in joiner transformation which we can not achieve in source qualifier transformation.
You need matching keys to join two relational sources in source qualifier transformation.Where as you doesn’t need matching keys to join two sources.
Two relational sources should come from same datasource in sourcequalifier.You can join relatinal sources which are coming from diffrent sources also.
Q:What is aggregate cache in aggregator transforamtion?
A:The aggregator stores data in the aggregate cache until it completes aggregate calculations.When you run a session that uses an aggregator transformation,
the informatica server creates index and data caches in memory to process the transformation.If the informatica server requires more space,
it stores overflow values in cache files.
Q:Can you use the maping parameters or variables created in one maping into any other reusable transformation?
A:Yes.Because reusable tranformation is not contained with any maplet or maping.
Q:Can you use the maping parameters or variables created in one maping into another maping?
A:No.
Q:What are the mapping paramaters and maping variables?
A:Maping parameter represents a constant value that You can define before running a session.A mapping parameter retains the same value throughout the entire session.
When you use the mapping parameter ,U declare and use the parameter in a mapping or maplet.Then define the value of parameter in a parameter file for the session.
Unlike a mapping parameter,a maping variable represents a value that can change throughout the session.The informatica server saves the value of maping variable to the
repository at the end of session run and uses that value next time you run the session.
Q:What are the reusable transformations?
A:Reusable transformations can be used in multiple mappings.When you need to incorporate this transformation into maping,U add an instance of it to maping.
Later if you change the definition of the transformation ,all instances of it inherit the changes.Since the instance of reusable transforamation is a pointer
to that transforamtion,You can change the transforamation in the transformation developer,its instances automatically reflect these changes.
This feature can save you great deal of work.
Q:What are the active and passive transforamtions?
A:An active transforamtion can change the number of rows that pass through it.
A passive transformation does not change the number of rows that pass through it.
A:Type1: Rows containing changes to existing dimensions are updated in the target by overwriting the existing dimension. In the Type 1 Dimension mapping, all rows contain
current dimension data.
Use the Type 1 Dimension mapping to update a slowly changing dimension table when you do not need to keep any previous versions of dimensions in the table.
Type 2: The Type 2 Dimension Data mapping inserts both new and changed dimensions into the target. Changes are tracked in the target table by versioning the primary
key and creating a version number for each dimension in the table.
Use the Type 2 Dimension/Version Data mapping to update a slowly changing dimension table when you want to keep a full history of dimension data in the table.
Version numbers and versioned primary keys track the order of changes to each dimension.
Type 3: The Type 3 Dimension mapping filters source rows based on user-defined comparisons and inserts only those found to be new dimensions to the target. Rows
containing changes to existing dimensions are updated in the target. When updating an existing dimension, the Informatica Server saves existing data in different columns
of the same row and replaces the existing data with the updates.
Q:What are the basic needs to join two sources in a source qualifier?
A:Two sources should have primary and Foreign key relation ships.
Two sources should have matching data types.
Q:What is the Default Join that source Qualifier Provides?
A:Inner equi join.
Q:What is the status code?
A:Status code provides error handling for the informatica server during the session.The stored procedure issues a status code that notifies whether or not stored procedure
completed sucessfully.This value can not seen by the user.It only used by the informatica server to determine whether to continue running the session or stop.
Q:Differences between connected and unconnected lookup?
A:Connected lookup:-
1> Receives input values diectly from the pipe line.
2> You can use a dynamic or static cache.
3> Cache includes all lookup columns used in the maping.
4> Support user defined default values.
Unconnected lookup:-
1> Receives input values from the result of a lkp expression in a another transformation.
2> You can use a static cache.
3> Cache includes all lookup out put ports in the lookup condition and the lookup/return port.
4> Does not support user defiend default values.
Q:Why use the lookup transformation?
A:To perform the following tasks:-
Get a related value. For example, if your source table includes employee ID, but you want to include the employee name in your target table to make your summary data
easier to read.
Perform a calculation. Many normalized tables include values used in a calculation, such as gross sales per invoice or sales tax, but not the calculated value (such as net
sales).
Update slowly changing dimension tables. You can use a Lookup transformation to determine whether records already exist in the target.
Q:In which condtions we can not use joiner transformation(Limitaions of joiner transformation)?
A:Both pipelines begin with the same original data source.
Both input pipelines originate from the same Source Qualifier transformation.
Both input pipelines originate from the same Normalizer transformation.
Both input pipelines originate from the same Joiner transformation.
Either input pipelines contains an Update Strategy transformation.
Either input pipelines contains a connected or unconnected Sequence Generator transformation.
Q:What are the diffrence between joiner transformation and source qualifier transformation?
A:You can join hetrogenious data sources in joiner transformation which we can not achieve in source qualifier transformation.
You need matching keys to join two relational sources in source qualifier transformation.Where as you doesn’t need matching keys to join two sources.
Two relational sources should come from same datasource in sourcequalifier.You can join relatinal sources which are coming from diffrent sources also.
Q:What is aggregate cache in aggregator transforamtion?
A:The aggregator stores data in the aggregate cache until it completes aggregate calculations.When you run a session that uses an aggregator transformation,
the informatica server creates index and data caches in memory to process the transformation.If the informatica server requires more space,
it stores overflow values in cache files.
Q:Can you use the maping parameters or variables created in one maping into any other reusable transformation?
A:Yes.Because reusable tranformation is not contained with any maplet or maping.
Q:Can you use the maping parameters or variables created in one maping into another maping?
A:No.
Q:What are the mapping paramaters and maping variables?
A:Maping parameter represents a constant value that You can define before running a session.A mapping parameter retains the same value throughout the entire session.
When you use the mapping parameter ,U declare and use the parameter in a mapping or maplet.Then define the value of parameter in a parameter file for the session.
Unlike a mapping parameter,a maping variable represents a value that can change throughout the session.The informatica server saves the value of maping variable to the
repository at the end of session run and uses that value next time you run the session.
Q:What are the reusable transformations?
A:Reusable transformations can be used in multiple mappings.When you need to incorporate this transformation into maping,U add an instance of it to maping.
Later if you change the definition of the transformation ,all instances of it inherit the changes.Since the instance of reusable transforamation is a pointer
to that transforamtion,You can change the transforamation in the transformation developer,its instances automatically reflect these changes.
This feature can save you great deal of work.
Q:What are the active and passive transforamtions?
A:An active transforamtion can change the number of rows that pass through it.
A passive transformation does not change the number of rows that pass through it.
posted by dwhfaq | 2:05 PM
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