Informatica Data Quality Interview Questions
IDQ Interview Questions
What are the types of loading in Informatica?
There are two types of loading, normal loading and bulk loading. In normal loading, it loads record by record and writes log for that. It takes comparatively a longer time to load data to the target in normal loading. But in bulk loading, it loads number of records at a time to target database. It takes less time to load data to target.
What is aggregate cache in aggregator transformation?
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.
How can you define a transformation? What are different types of transformations available in Informatica?
A transformation is a repository object that generates, modifies, or passes data. The Designer provides a set of transformations that perform specific functions. For example, an Aggregator transformation performs calculations on groups of data. Below are the various transformations available in Informatica:
What is Surrogate key?
Surrogate key is a substitution for the natural primary key. It is just a unique identifier or number of each row that can be used for the primary key to the table.
Define Informatica repository?
Informatica Repository:The Informatica repository is at the center of the Informatica suite. You create a set of metadata tables within the repository database that the Informatica application and tools access. The Informatica client and server access the repository to save and retrieve metadata.
What are the tasks that source qualifier performs?
Join data originating from same source database. Filter records when the informatica server reads source data. Specify an outer join rather than the default inner join specify sorted records. Select only distinct values from the source. Creating custom query to issue a special SELECT statement for the informatica server to read source data.
What is the target load order?
Specify the target load order based on source qualifiers in a mapping. If you have the multiple source qualifiers connected to the multiple targets you can designate the order in which informatica server loads data into the targets.
How Union Transformation is used?
The union transformation is a multiple input group transformation that can be used to merge data from various sources (or pipelines). This transformation works just like UNION ALL statement in SQL, that is used to combine result set of two SELECT statements.
Can two flat files be joined with Joiner Transformation?
Yes, joiner transformation can be used to join data from two flat file sources.
What is a look up transformation?
This transformation is used to lookup data in a flat file or a relational table, view or synonym. It compares lookup transformation ports (input ports) to the source column values based on the lookup condition. Later returned values can be passed to other transformations.
Which transformation should you need while using the cobol sources as source definitions?
Normalizer transformation which is used to normalize the data. Since COBOL sources are often consists of Denormalized data.
What is the difference between a connected lookup and unconnected lookup?
Connected lookup takes input values directly from other transformations in the pipeline.
Unconnected lookup doesn't take inputs directly from any other transformation, but it can be used in any transformation (like expression) and can be invoked as a function using :LKP expression. So, an unconnected lookup can be called multiple times in a mapping.
What are the types of data that passes between informatica server and stored procedure?
3 types of data
- Input/Output parameters
- Return Values
- Status code.
What is the status code?
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 successfully. 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.
What is source qualifier transformation?
When you add a relational or a flat file source definition to a mapping, you need to connect it to a source qualifier transformation. The source qualifier transformation represents the records that the informatica server reads when it runs a session.
How many types of dimensions are available in Informatica?
There are three types of dimensions available are :
- Junk dimension
- Degenerative Dimension
- Conformed Dimension
What is the maplet?
Maplet is a set of transformations that you build in the maplet designer and you can use in multiple mappings
What is Session and Batches?
A session is a set of commands that describes the server to move data to the target.
A Batch is set of tasks that may include one or more number of tasks (sessions, event wait, email, command, etc).
What are slowly changing dimensions?
Dimensions that change over time are called Slowly Changing Dimensions(SCD).
Slowly Changing Dimension-Type 1 : Which has only current records.
Slowly Changing Dimension-Type2 : Which has current records + historical records.
Slowly Changing Dimension-Type3 : Which has current records + one previous records.
What is the difference between Active and Passive transformation?
Active Transformation:An active transformation can change the number of rows that pass through it from source to target i.e it eliminates rows that do not meet the condition in transformation.
Passive Transformation:A passive transformation does not change the number of rows that pass through it i.e it passes all rows through the transformation.
What are Aggregator Transformation?
Aggregator transformation is an Active and Connected transformation. This transformation is useful to perform calculations such as averages and sums (mainly to perform calculations on multiple rows or groups).
What are Expression transformation?
Expression transformation is a Passive and Connected transformation. This can be used to calculate values in a single row before writing to the target.
What are Filter transformation?
Filter transformation is an Active and Connected transformation. This can be used to filter rows in a mapping that do not meet the condition.
What are Joiner transformation?
Joiner Transformation is an Active and Connected transformation. This can be used to join two sources coming from two different locations or from same location.
Why we use lookup transformations?
Lookup Transformations can access data from relational tables that are not sources in mapping.
What are Normalizer transformation?
Normalizer Transformation is an Active and Connected transformation. It is used mainly with COBOL sources where most of the time data is stored in denormalized format. Also, Normalizer transformation can be used to create multiple rows from a single row of data.
What are Rank transformation?
Rank transformation is an Active and Connected transformation. It is used to select the top or bottom rank of data.
What are Router transformation?
Router transformation is an Active and Connected transformation. It is similar to filter transformation. The only difference is, filter transformation drops the data that do not meet the condition whereas router has an option to capture the data that do not meet the condition. It is useful to test multiple conditions.
What are Sorter transformation?
Sorter transformation is a Connected and an Active transformation. It allows to sort data either in ascending or descending order according to a specified field
Name four output files that information server creates during session running?
Session Log ,Workflow Log,Errors Log, Badfile
Why we use stored procedure transformation?
A stored procedure transformation is an important tool for populating and maintaing databases.
What are the difference between static cache and dynamic cache?
Dynamic cache decreases the performance in comparision to static cache.
Static cache do not see such things just insert data as many times as it is coming
Define mapping and sessions?
It is a set of source and target definitions linked by transformation objects that define the rules for transformation.
It is a set of instructions that describe how and when to move data from source to targets.
What is a command that used to run a batch?
pmcmd is used to start a batch.
What is Datadriven?
The informatica server follows instructions coded into update strategy transformations with in the session maping determine how to flag records for insert, update, delete or reject.
What is power center repository?
The PowerCenter repository allows you to share metadata across repositories to create a data mart domain.
What is parameter file?
A parameter file is a file created by text editor such as word pad or notepad. U can define the following values in parameter file.
- Maping parameters
- Maping variables
- session parameters.
What are the types of lookup caches?
Static cache Dynamic cache Persistent cache Shared cache Recache.
What are the differences between Connected and Unconnected Lookup?
|Connected Lookup||Unconnected Lookup|
|Connected lookup participates in dataflow and receives input directly from the pipeline||Unconnected lookup receives input values from the result of a LKP: expression in another transformation|
|Connected lookup can use both dynamic and static cache||Unconnected Lookup cache can NOT be dynamic|
|Connected lookup can return more than one column value ( output port )||Unconnected Lookup can return only one column value i.e. output port|
|Connected lookup caches all lookup columns||Unconnected lookup caches only the lookup output ports in the lookup conditions and the return port|
|Unconnected lookup caches only the lookup output ports in the lookup conditions and the return port||Supports user-defined default values (i.e. value to return when lookup conditions are not satisfied)|
What is fact table?
The centralized table in a star schema is called as fact table. Fact tables are three types
Additive non-additive semi additive
What is Data warehouse?
According to Bill Inmon, known as father of Data warehousing. “A Data warehouse is a subject oriented, integrated ,time variant, non volatile collection of data in support of management’s decision making process”.
What is Data Transformation Manager(DTM)?
After the load manager performs validations for the session, it creates the DTM process. The DTM process is the second process associated with the session run.
How can you define a transformation?
A transformation is a repository object that generates, modifies, or passes data. The Designer provides a set of transformations that perform specific functions.
What are Lookup transformation?
Lookup transformation is Passive and it can be both Connected and UnConnected as well. It is used to look up data in a relational table, view, or synonym. Lookup definition can be imported either from source or from target tables.
What is difference between maplet and reusable transformation?
Maplet consists of set of transformations that is reusable.
A reusable transformation is a single transformation that can be reusable.
What are Update Strategy transformation?
Update strategy transformation is an active and connected transformation. It is used to update data in target table, either to maintain history of data or recent changes. You can specify how to treat source rows in table, insert, update, delete or data driven.
Informatica Data Quality Interview Questions
What is the difference between Router and Filter?
|Router transformation divides the incoming records into multiple groups based on some condition. Such groups can be mutually inclusive (Different groups may contain same record)||Filter transformation restricts or blocks the incoming record set based on one given condition.|
|Filter transformation restricts or blocks the incoming record set based on one given condition.||Filter transformation does not have a default group. If one record does not match filter condition, the record is blocked|
|Router acts like CASE.. WHEN statement in SQL (Or Switch().. Case statement in C)||Router acts like CASE.. WHEN statement in SQL (Or Switch().. Case statement in C)|
What is update strategy and what are the options for update strategy?
Informatica processes the source data row-by-row. By default every row is marked to be inserted in the target table. If the row has to be updated/inserted based on some logic Update Strategy transformation is used. The condition can be specified in Update Strategy to mark the processed row for update or insert.
Following options are available for update strategy :
|DD_INSERT||If this is used the Update Strategy flags the row for insertion. Equivalent numeric value of DD_INSERT is 0.|
|DD_UPDATE||If this is used the Update Strategy flags the row for update. Equivalent numeric value of DD_UPDATE is 1.|
|DD_DELETE||If this is used the Update Strategy flags the row for deletion. Equivalent numeric value of DD_DELETE is 2.|
|DD_REJECT||If this is used the Update Strategy flags the row for rejection. Equivalent numeric value of DD_REJECT is 3.|
What can we do to improve the performance of Informatica Aggregator Transformation?
Aggregator performance improves dramatically if records are sorted before passing to the aggregator and "sorted input" option under aggregator properties is checked. The record set should be sorted on those columns that are used in Group By operation.
What are the different lookup cache(s)?
Informatica Lookups can be cached or uncached (No cache). And Cached lookup can be either static or dynamic. A static cache is one which does not modify the cache once it is built and it remains same during the session run. On the other hand, A dynamic cache is refreshed during the session run by inserting or updating the records in cache based on the incoming source data. By default, Informatica cache is static cache.
Lookup cache can also be divided as persistent or nonpersistent based on whether Informatica retains the cache even after the completion of session run or deletes it
How can we update a record in target table without using Update strategy?
A target table can be updated without using 'Update Strategy'. For this, we need to define the key in the target table in Informatica level and then we need to connect the key and the field we want to update in the mapping Target. In the session level, we should set the target property as "Update as Update" and check the "Update" check-box.
What is the difference between Static and Dynamic Lookup Cache?
We can configure a Lookup transformation to cache the underlying lookup table. In case of static or read-only lookup cache the Integration Service caches the lookup table at the beginning of the session and does not update the lookup cache while it processes the Lookup transformation.
In case of dynamic lookup cache the Integration Service dynamically inserts or updates data in the lookup cache and passes the data to the target. The dynamic cache is synchronized with the target.
In case you are wondering why do we need to make lookup cache dynamic, read this article on dynamic lookup
Let's assume we have a target table "Customer" with fields as "Customer ID", "Customer Name" and "Customer Address". Suppose we want to update "Customer Address" without an Update Strategy. Then we have to define "Customer ID" as primary key in Informatica level and we will have to connect Customer ID and Customer Address fields in the mapping. If the session properties are set correctly as described above, then the mapping will only update the customer address field for all matching customer IDs.
Why is Sorter an Active Transformation?
This is because we can select the "distinct" option in the sorter property.
When the Sorter transformation is configured to treat output rows as distinct, it assigns all ports as part of the sort key. The Integration Service discards duplicate rows compared during the sort operation. The number of Input Rows will vary as compared with the Output rows and hence it is an Active transformation.
Is lookup an active or passive transformation?
From Informatica 9x, Lookup transformation can be configured as as "Active" transformation.
What is the difference between STOP and ABORT options in Workflow Monitor?
When we issue the STOP command on the executing session task, the Integration Service stops reading data from source. It continues processing, writing and committing the data to targets. If the Integration Service cannot finish processing and committing data, we can issue the abort command.
In contrast ABORT command has a timeout period of 60 seconds. If the Integration Service cannot finish processing and committing data within the timeout period, it kills the DTM process and terminates the session.
When we install the informatica powercenter, the following components gets installed?
- powercenter clients
- Integration service
- powercenter Repository service
- powercenter Repository
- powercenter Domain
- powercenter Administration console