Barclays Informatica Interview Questions
1. What is a data warehouse?
- The data warehouse is a technique of integrating data from multiple sources. It involves analytical reporting, data integration, data cleaning, and data consolidations.
- A data warehouse is mainly designed for query and data analysis purpose instead of transaction processing.
- It is used to transform the information into useful data whenever the user required.
- The data warehouse is an environment, not a product that provides the current and historical decision support information to the users, which is not possible to access the traditional operational database.
- The data which is processed and transformed in the data warehouse can be accessed by using the Business Intelligence tools, SQL Clients, and spreadsheets.
2. What is the difference between active and passive transformation?
An active transformation is a transformation that changes the number of rows when the source table is passed through it. For example, Aggregator transformation is a type of active transformation that performs the aggregations on groups such as sum and reduces the number of rows.
A passive transformation is a transformation that does not change the number of rows when the source data is passed through it, i.e., neither the new rows are added, nor existing rows are dropped. In this transformation, the number of output and input rows are the same.
3. What is repository manager?
A repository is a place or a relational database used to store the information or metadata. Metadata can include various information such as mappings that describes how to transform the data, sessions describe when you want the Informatica server to perform the transformations, also stores the administrative information such username and password, permissions and privileges, and product version. The repository is created and maintained by the Repository Manager client tool.
Repository Manager is a manager that manages and organizes the repository. Repository Manager can create the folders to organize the data and groups to handle multiple users.
4. How are indexes created after completing the load process?
For the purpose of creating indexes after the load process, command tasks at session level can be used. Index creating scripts can be brought in line with the session’s workflow or the post session implementation sequence. Moreover this type of index creation cannot be controlled after the load process at transformation level.
5. Explain sessions. Explain how batches are used to combine executions?
A teaching set that needs to be implemented to convert data from a source to a target is called a session. Session can be carried out using the session’s manager or pmcmd command. Batch execution can be used to combine sessions executions either in serial manner or in a parallel. Batches can have different sessions carrying forward in a parallel or serial manner.
6. Briefly describe lookup transformation?
Lookup transformations are those transformations which have admission right to RDBMS based data set. The server makes the access faster by using the lookup tables to look at explicit table data or the database. Concluding data is achieved by matching the look up condition for all look up ports delivered during transformations.
7. Explain the code page compatibility?
When data moves from one code page to another provided that both code pages have the same character sets then data loss cannot occur. All the characteristics of source page must be available in the target page. Moreover if all the characters of source page are not present in the target page then it would be a subset and data loss will definitely occur during transformation due the fact the two code pages are not compatible.
8. What is Joiner transformation?
Joiner transformation combines two affiliated heterogeneous sources living in different locations while a source qualifier transformation can combine data emerging from a common source.
9. What is Lookup transformation?
It is used for looking up data in a relational table through mapping. Lookup definition from any relational database is imported from a source which has tendency of connecting client and server. One can use multiple lookup transformation in a mapping.
10. What is the difference between a connected look up and unconnected look up?
When the inputs are taken directly from other transformations in the pipeline it is called connected lookup. While unconnected lookup doesn’t take inputs directly from other transformations, but it can be used in any transformations and can be raised as a function using LKP expression. So it can be said that an unconnected lookup can be called multiple times in mapping.
11. What is meant by pre and post session shell command?
Command task can be called as the pre or post session shell command for a session task. One can run it as pre session command r post session success command or post session failure command.
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