1.What is ETL Process?
ETL is the process of Extraction, Transforming, and Loading.
2.How many steps are there in ETL process?
In ETL process data is extracted from the source such as the database servers and it is used to generate business roll.
3.What are the steps involved in ETL process?
The steps involved are defining the source; target, creating the mapping, creating the session, and creating the workflow.
4.Can there be sub-steps of ETL steps?
Each of the steps involved in ETL has several sub-steps. The data transformation step has most sub-steps.
5.What is initial load and what is full load?
In ETL, the initial load is the process for populating all data warehousing tables for very first time. Full load means when the data is loaded for the first time all set records are loaded at a stretch depending on its volume. It would erase all contents in the table and would reload fresh data.
6.What is meant by incremental load?
Incremental load refers to applying the dynamic changes as and when required in a specific period and predefined schedules.
7.What are three tier systems in ETL?
The data warehouse is considered to be the three tier system in ETL.
8.What are the three tiers in ETL?
Middle layer in ETL provides the data that is usable in a secure way to end users. Other two layers are on the other side of the middle tier, the end user and back end data storage.
9.What are the names of the layers in ETL?
The first layer in ETL is the source layer and it is the layer where data lands. The second layer is integration layer where data is stored after transformation. The third layer is the dimension layer where actual presentation layer stands.
10.What is meant by snapshots?
Snapshots are the copies of read-only data that is stored in the master table.
11.What are the characteristics of Snapshots?
Snapshots are located on the remote node and refreshed periodically so that the changes in the master table can be recorded. They are also the replica of tables.
12.What are views?
Views are built using the attributes of one or more tables. View with single tables can be updated but those with multiple tables cannot be updated.
13.What is meant by materialized view log?
Materialized view log is the pre-computed table with aggregated or joined data from the fact tables as well as the dimension tables.
14.What is a materialized view?
Materialized view is an aggregate table.
15.What is the difference between power center and power mart?
Task accomplished by Power Center is processing large volumes of data. Power Mart processes low volumes of data.
16.With which apps can Power Center be connected?
Power Center can be connected with ERP source like the SAP, Oracle Apps, and the People Soft etc.
17.Which partition is used to improve the performances of ETL transactions?
To improve the performances of ETL transactions the session partition is used.
18.Does Power Mart provide connections to ERP sources?
No! Power Mart does not provide connection to any of the ERP sources. It also does not allow sessions partition.
19.What is meant by partitioning in ETL?
Partitioning in ETL refers to the subdivision of the transactions in order to improve their performances.
20.What is the benefit of increasing number of partitions in ETL?
The increase in the number of partitions enables the informatics Server to create multiple connections to a host of sources.
21.What are the types of partitions in Informatica?
Types of partitions in ETL are Round-Robin partition and Hash partition.
22.What is Round Robin partitioning?
In Round Robin partitioning the data is evenly distributed by the Informatica among all the partitions. It is used when the number of rows in the process in each of the partitions is nearly the same.
23.What is Hash partitioning?
In Hash partitioning, the Informatica server would apply a hash function in order to partition keys to group data among the partitions. It is used to ensure the processing of a group of rows with the same partitioning key in the same partition.
24.What is mapping in Informatica?
Mapping refers to the flow of data from source to the destination.
25.What is a session in Informatica?
A Session is a set of instructions that describes the data movement from the source to the destination.
26.What is meant by Worklet in Informatica?
A Worklet is the set of tasks in Informatica which can be reused in other workflows to achieve the same functionality. It can be any set of tasks in the program.
27.What is workflow in Informatica?
Workflow is a set of instruction that specifies the way of executing the tasks to the Informatica Integration Service.
28.What is referred by Mapplet in Informatica?
Mapplet in ETL is used for the purpose of creation as well as the configuration of a group of transformations. However, it cannot contain any Target within it.
29.What is meant by operational data store?
The operational data store is the repository that exists between the staging area and the data warehouse. Data stored in ODS has low granularity.
30.How operational data store works?
Aggregated data is loaded into the EDW after it is populated in the operational data store or ODS. Basically, ODS is also semi DWH helping analysis of business data. Data persistence period in ODS is usually in the range of 30-45 days and not more.
31.What the ODS in ETL generates?
ODS in ETL generates primary keys, takes care of the error
32.How can the mapping be fine tuned in Informatica?
Steps for fine tuning the mapping involves using condition for filter in source qualifying the data without use of filter; utilizing persistence as well as cache store in Lookup transformation; using the Aggregator transformation in sorted input group by different ports, using operators in expressions instead of functions, and increase the cache size and setting the optimized commit interval.
33.What are differences between connected and unconnected look up in Informatica?
Connected Lookup is used for mapping and can have more than one return port. It is connected to other transformations and is part of the main flow. Unconnected Lookup is used to call Lookup table based on required conditions and have only single return port. It is not connected to any transformation but are reusable.
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