Wednesday, 11 February 2015

Data Warehousing Cognos Interview Questions and Answers (Page 6)

Below are some important Cognos interview questions which are asked in most MNC company interviews for beginners or professionals.

51. How do you call a store procedure within a transformation?
In the expression transformation create new out port in the expression write :sp.stored procedure name(arguments).

52. What is difference between Informatica power mart and power center?
Using power center we can create global repository
Power mart used to create local repository
Global repository configure multiple server to balance session load
Local repository configure only single server

53. What are the batches and it’s details?
Sequential(Run the sessions one by one
Concurrent (Run the sessions simultaneously)

54. What is main difference mapplets and mapping?
Reuse the transformation in several mappings, where as mapping not like that.
If any changes made in mapplets it automatically inherited in all other instance mapplets.

55. Source table has 5 rows. Rank in rank transformation is set to 10. How many rows the rank transformation will output?
5 Rank.

56. What is bitmap index?
A bitmap for each key value replaces a list of rowids. Bitmap index more efficient for data warehousing because low cardinality, low updates, very efficient for where class.

57. Why need staging area database for DWH?
Staging area needs to clean operational data before loading into data warehouse.
Cleaning in the sense your merging data which comes from different source

58. What is slowly changing dimension?
Dimension attribute values may change constantly over the time. (Say for example customer dimension has customer_id,name, and address) customer address may change over time.

59. What is difference between primary key and unique key constraints?
Primary key maintains uniqueness and not null values Where as unique constrains maintain unique values and null values.

60. What are the types of index?
Bitmap index ,B-tree index, Function based index ,reverse key and composite index. We used Bitmap index in our project for better performance.

61. What are the different uses of a repository manager?
Repository manager used to create repository which contains metadata the informatica uses to transform data from source to target. And also it use to create informatica user’s and folders and copy, backup and restore the repository.

62. What are shortcuts? Where it can be used? What are the advantages?
There are 2 shortcuts(Local and global) Local used in local repository and global used in global repository. The advantage is reuse an object without creating multiple objects. Say for example a source definition want to use in 10 mappings in 10 different folder without creating 10 multiple source you create 10 shotcuts.
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