1. Explain What is ODS (operation data source)?
ODS - Operational Data Store.
ODS Comes between staging area & Data Warehouse. The data is ODS will be at the low level of granularity.
Once data was poopulated in ODS aggregated data will be loaded into into EDW through ODS.
ODS: ODS is also a simalar small DWH which will help analyst to analysis the bussiness.It will have data for less number of days. generally it will be around 30-45 days. Like DWH here also we will primary keys will be genrated, error and reject handling will be done.
2. Explain if a flat file cotains 1000 records how can i get first and last records only?
By using Aggregator transformation with first and last functions we can get first and last record.
3. What are the various tools? Explain Name a few?
A few more ...
- Cognos Decision Stream
- Oracle Warehouse Builder
- Business Objects XI (Extreme Insight)
- SAP Business Warehouse
- SAS Enterprise ETL Server
Tools of SAS are :-
- SAS Information delivery portal.
- SAS data integration studio.
- Business Intelligence.
-SAS Enterprise Guide.
4. What is latest version of Power Center / Power Mart?
he Latest Version is 7.2
informatica 8.0
5. How to calculate fact table granularity?
Granularity , is the level of detail in which the fact table is describing, for example if we are making time analysis so the granularity maybe day based - month based or year based
6. Explain What are the modules in Power Mart?
1. PowerMart Designer
2. Server
3. Server Manager
4. Repository
5. Repository Manager
7. How to extract SAP data Using Informatica? What is ABAP? What are IDOCS?
SAP Data can be loaded into Informatica in the form of Flat files.
Condition :
Informatica source qualifier column sequence must match the SAP source file.
8. Explain the difference between etl tool and olap tools?
ETL tool is ment for extraction data from the legecy systems and load into specified data base with some process of cleansing data.
ex: Informatica,data stage ....etc
OLAP is ment for Reporting purpose.in OLAP data avaliable in Mulitidimectional model. so that u can write smple query to extract data fro the data base.
ex: Businee objects,Cognos....etc
9. Explain What are the various transformation available?
Aggregator Transformation
Expression Transformation
Filter Transformation
Joiner Transformation
Lookup Transformation
Normalizer Transformation
Rank Transformation
Router Transformation
Sequence Generator Transformation
Stored Procedure Transformation
Sorter Transformation
Update Strategy Transformation
XML Source Qualifier Transformation
Advanced External Procedure Transformation
External Transformation
There are various ways of Extracting Data from Source Systems.For example , You can use a DATA step, an Import Process .It depends with your input data styles. What kind of File/database it is residing in. Storing ur data in an ODS can be done thru an ODS stmt/export stmt/FILE stmt, again which depends on the file & data format ,You want your output to be in.
Rejection of records either at the database due to constraint key violation or the informatica server when writing data into target table.These rejected records we can find in the badfiles folder where a reject file will be created for a session.we can check why a record has been rejected.And this bad file contains first column a row indicator and second column a column indicator.
These row indicators or of four types
D-valid data,
O-overflowed data,
N-null data,
T- Truncated data,
And depending on these indicators we can changes to load data successfully to target.
12. Explain What are the different versions of Informatica?
Here are some popular versions of Informatica.
Informatica Powercenter 4.1, Informatica Powercenter 5.1, Powercenter Informatica 6.1.2, Informatica Powercenter 7.1.2, Informatica Powercenter 8.1, Informatica Powercenter 8.5, Informatica Powercenter 8.6.
You can verify the session log and ensure the source fetched and target loaded details
14. Explain When do we Analyze the tables? How do we do it?
The ANALYZE statement allows you to validate and compute statistics for an index, table, or cluster. These statistics are used by the cost-based optimizer when it calculates the most efficient plan for retrieval. In addition to its role in statement optimization, ANALYZE also helps in validating object structures and in managing space in your system. You can choose the following operations: COMPUTER, ESTIMATE, and DELETE. Early version of Oracle7 produced unpredicatable results when the ESTIMATE operation was used. It is best to compute
your statistics.
EX:
select OWNER,
sum(decode(nvl(NUM_ROWS,9999), 9999,0,1)) analyzed,
sum(decode(nvl(NUM_ROWS,9999), 9999,1,0)) not_analyzed,
count(TABLE_NAME) total
from dba_tables
where OWNER not in ('SYS', 'SYSTEM')
group by OWNER
15. Explain and Compare ETL & Manual development?
ETL - The process of extracting data from multiple sources.(ex. flat files,XML, COBOL, SAP etc) is more simpler with the help of tools.
Manual - Loading the data other than flat files and oracle table need more effort.
ETL - High and clear visibilty of logic.
Manual - complex and not so user friendly visibilty of logic.
ETL - Contains Meta data and changes can be done easily.
Manual - No Meta data concept and changes needs more effort.
ETL- Error hadling,log summary and load progess makes life easier for developer and maintainer.
Manual - need maximum effort from maintainance point of view.
ETL - Can handle Historic data very well.
Manual - as data grows the processing time degrads.
These are some differences b/w manual and ETL developement.
16. Explain the difference between keylokup and joiner?
Explain your self
he best procedure to take a help of debugger where we monitor each and every process of mappings and how data is loading based on conditions breaks.
18. Explain the different Lookup methods used in Informatica?
1. Connected lookup
2. Unconnected lookup
Connected lookup will receive input from the pipeline and sends output to the pipeline and can return any number of values.it does not contain retun port.
Unconnected lookup can return only one column. it containn return port.
19. How can we determine what records to extract?
When addressing a table some dimension key must reflect the need for a record to get extracted. Mostly it will be from time dimension (e.g. date >= 1st of current mth) or a transaction flag (e.g. Order Invoiced Stat). Foolproof would be adding an archive flag to record which gets reset when record changes.
20. Explain Where do we use semi and non additive facts?
Additve: A masure can participate arithmatic calulatons using all or any demensions.
Ex: Sales profit
Semi additive: A masure can participate arithmatic calulatons using some demensions.
Ex: Sales amount
Non Additve:A masure can't participate arithmatic calulatons using demensions.
Ex: temparature
21. Explain What is the difference between Power Center & Power Mart?
PowerCenter - ability to organize repositiries into a data mart domain and share metadata across repositiries.
PowerMart - only local repositiry can be created.
22. Explain What is a three tier data warehouse?
A data warehouse can be thought of as a three-tier system in which a middle system provides usable data in a secure way to end users. On either side of this middle system are the end users and the back-end data stores.
23. Tell me what is Full load & Incremental or Refresh load?
Full Load: completely erasing the contents of one or more tables and reloading with fresh data.
Incremental Load: applying ongoing changes to one or more tables based on a predefined schedule
Refresh Load: the table will be truncated and data will be loaded again. Here we use to load static dimension table or type tables using this method.
Incremental Load: It is a method to capture on the newly created or updated record. Based upon the falg or Date this load will be performed.
Full Load: when we are loading the data for first time, either it may be a base load or history all the set of records will be loaded at a strech depends upon the volume.
24. Explain a mapping, session, worklet, workflow, mapplet?
A mapping represents dataflow from sources to targets.
A mapplet creates or configures a set of transformations.
A workflow is a set of instruction sthat tell the Informatica server how to execute the tasks.
A worklet is an object that represents a set of tasks.
A session is a set of instructions that describe how and when to move data from sources to targets.
25. Explain What is Full load & Incremental or Refresh load?
Full Load: completely erasing the contents of one or more tables and reloading with fresh data.
Incremental Load: applying ongoing changes to one or more tables based on a predefined schedule.
first time what we are loading the data is called initial load or full load.
secondtime or modified data waht ewe are loading is called as incremental load or delta load.
26. Explain What is a staging area? Do we need it? What is the purpose of a staging area?
Data staging is actually a collection of processes used to prepare source system data for loading a data warehouse. Staging includes the following steps:
Source data extraction, Data transformation (restructuring),
Data transformation (data cleansing, value transformations),
Surrogate key assignments
One foolproof method is to maintain a field called 'Last Extraction Date' and then impose a condition in the code saying 'current_extraction_date > last_extraction_date'.
First Method: If there is a column in the source which identifies the record inserted date. Then it will be easy to put a filter condition in the source qualifier.
Second Method: If there is no record in the source to identify the record inserted date. Then we need to do a target lookup based on the primary key and determine the new record and then insert.
Yes,we can override a native sql query in source qualifier and lookup transformation.
In lookup transformation we can find "Sql override" in lookup properties.by using this option we can do this.
Snapshots are read-only copies of a master table located on a remote node which is periodically refreshed to reflect changes made to the master table. Snapshots are mirror or replicas of tables.
Views are built using the columns from one or more tables. The Single Table View can be updated but the view with multi table cannot be updated.
A View can be updated/deleted/inserted if it has only one base table if the view is based on columns from one or more tables then insert, update and delete is not possible.
Materialized view
A pre-computed table comprising aggregated or joined data from fact and possibly dimension tables. Also known as a summary or aggregate table.
we cant directly import the xml file in informatica.
we have to define the microsoft excel odbc driver on our system. and define the name in exce sheet by defining ranges.
then in inforematica open the folder using sources ->import from database->select excel odbc driver->connect->select the excel sheet name .
31. Explain What is the metadata extension?
Informatica allows end users and partners to extend the metadata stored in the repository by associating information with individual objects in the repository. For example, when you create a mapping, you can store your contact information with the mapping. You associate information with repository metadata using metadata extensions.
Informatica Client applications can contain the following types of metadata extensions:
Vendor-defined. Third-party application vendors create vendor-defined metadata extensions. You can view and change the values of vendor-defined metadata extensions, but you cannot create, delete, or redefine them.
User-defined. You create user-defined metadata extensions using PowerCenter/PowerMart. You can create, edit, delete, and view user-defined metadata extensions. You can also change the values of user-defined extensions.
32. How to call shell scripts from informatica?
Specify the Full path of the Shell script the "Post session properties
of session/workflow".
33. Explain What is ETL process ?How many steps ETL contains explain with example?
ETL is extraction , transforming , loading process , you will extract data from the source and apply the business role on it then you will load it in the target
the steps are :
1-define the source(create the odbc and the connection to the source DB)
2-define the target (create the odbc and the connection to the target DB)
3-create the mapping ( you will apply the business role here by adding transformations , and define how the data flow will go from the source to the target )
4-create the session (its a set of instruction that run the mapping , )
5-create the work flow (instruction that run the session)
34. Explain What is Informatica Metadata and where is it stored?
Informatica Metadata is data about data which stores in Informatica repositories.
35. Explain Do we need an ETL tool? When do we go for the tools in the market?
ETL Tool:
It is used to Extract(E) data from multiple source systems(like RDBMS,Flat files,Mainframes,SAP,XML etc) transform(T) them based on Business requirements and Load(L) in target locations.(like tables,files etc).
Need of ETL Tool:
An ETL tool is typically required when data scattered accross different systems.(like RDBMS,Flat files,Mainframes,SAP,XML etc).