Ab Initio Interview Questions

1. What are the components of Ab Initio architecture?

Ans: Ab Initio's architecture encompasses several key components that work in unison to facilitate robust data processing and integration:

• Co>Operating System (Co>Op): This foundational layer sits atop the host operating system, enabling Ab Initio processes to run seamlessly across different environments like Windows, Linux, Solaris, etc.
• Component Library: A comprehensive collection of modules and tools for building and managing ETL (Extract, Transform, Load) processes.
• Graphical Development Environment (GDE): An intuitive interface for designing, editing, and managing Ab Initio data processing graphs.
• Enterprise Meta>Environment (EME): A central repository for metadata management, providing tools for data lineage, version control, and impact analysis.
• Data Profiler: An analytical tool for assessing data quality and structure within the ETL process.
• Conduct>IT: A component for orchestrating and monitoring ETL jobs in complex enterprise environments.

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2. Tell me about the CoOperating system in Ab Initio.

Ans: The Co>Operating System is a pivotal component of Ab Initio's architecture, serving as a platform-agnostic base for all its processes. Compatible with a range of operating systems, including Windows, Linux, Solaris, AIX, HP-UX, and z/OS, it extends the functionality of these systems to support sophisticated ETL operations. Key functions include metadata management via interaction with the EME and efficient execution and control of Ab Initio graphs.

3. Explain the relation between eme, gde, and co-operating system.

Ans: These components interact closely within Ab Initio's architecture. The Co>Operating System forms the operational backbone, installed directly on the operating system. The EME acts as a comprehensive metadata repository, storing crucial data about the ETL processes. The GDE offers a graphical interface for designing and executing Ab Initio graphs, and it enables users to access EME metadata through a web browser or the command line of the Co>Operating System.

4. What do you mean by dependency analysis in Ab Initio?

Ans: Dependency analysis in Ab Initio is a meticulous process undertaken by the EME to identify and track dependencies within and between data processing graphs. It involves a thorough examination of how data is transformed and transmitted across various components and fields. This analysis includes two primary steps: translation and in-depth analysis of these dependencies.

5. How is Ab Initio EME segregated?

Ans: The EME in Ab Initio is divided into two main segments: the data integration portion and the user interface. The data integration part deals with the actual handling and processing of metadata, while the user interface provides an accessible means for users to interact with and retrieve metadata information.

6. What do you know about overflow errors?

Ans: Overflow errors in data processing, such as those that can occur in Ab Initio, typically arise when handling large datasets or performing substantial calculations. These errors occur when the data exceeds the allocated memory space, or when attempting to store data that surpasses the defined data type limits, such as storing a character beyond 8 bits.

7. How to connect EME to Ab Initio Server?

Ans: Connecting the EME to the Ab Initio server can be achieved through several methods, including:

• Setting the AB_AIR_ROOT environment variable.
• Utilizing 'Air' commands.
• Accessing the EME web interface at http://serverhost:[serverport]/abinitio.
• Connecting to the EME data store via the GDE.

8. What are the file extensions used in Ab Initio?

Ans: Ab Initio utilizes a variety of file extensions, each serving a specific purpose in the ETL process:

• .mp: Graph or graph component files.
• .mpc: Custom component or program files.
• .dbc: Database configuration or table files.
• .dat: General data files.
• .mdc: Dataset template or custom dataset component files.
• .ksh: Shell scripting files.
• .xfr: Transform function files.
• .dml: Data Manipulation Language or record format files.

9. What are the kinds of layouts that Ab Initio supports?

Ans: Ab Initio supports two primary layout types:

• Serial Layout: Where the level of parallelism is set to 1, indicating sequential processing.
• Parallel Layout: Where the level of parallelism is variable, dependent on the data partitioning scheme.

10. How to add default rules in the transformer?

Ans: To add default rules in a transformer component within Ab Initio, follow these steps:

Open the component's properties.

• Navigate to the 'Parameter' tab.
• Double-click on the 'Transform' parameter to open the transform editor.
• In the editor, select the 'Edit' menu, then choose 'Add Default Rules'.
• Select from options like 'Match Names' or 'Wildcard' to apply the appropriate rules.

11. What is a local lookup?

Ans: A local lookup in Ab Initio is a function designed for efficiency, particularly when dealing with partitioned multifiles. It is employed prior to the main lookup function call. This function operates on a partition-by-partition basis, depending on a specific key, and allows for loading data records into memory from the lookup file. This significantly speeds up data retrieval, as accessing memory is faster than retrieving data from a disk.

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12. What is the difference between a lookup file and lookup?

Ans: In Ab Initio, a lookup file refers to a physical file (often a Flat file) that stores lookup data, small enough to be entirely loaded into memory. On the other hand, a lookup is a component within an Ab Initio graph where data, accompanied by a key parameter, resides. This key parameter facilitates the retrieval of specific data from the lookup file.

13. What information does a .dbc file extension provide to connect to the database?

Ans: A .dbc file in Ab Initio provides crucial information for database connectivity, including:

The database's name and version number.

The system name where the database server or instance operates.

The server or database instance's name.

14. How can you execute a graph infinitely in Ab Initio?

Ans: To execute an Ab Initio graph infinitely, you can use a looping mechanism by invoking the graph's .ksh file at the end of its execution script. For example, if the graph's name is xyz.mp, the end script should include a call to xyz.ksh, creating a continuous execution cycle. 

15. Explain the different types of parallelism used in Ab Initio.

Ans:  Ab Initio employs three forms of parallelism to optimize data processing:

• • Component Parallelism: Multiple processes execute concurrently, each handling different data.
  • Data Parallelism: The data is segmented, and each segment is processed independently.
  • Pipeline Parallelism: Multiple components work simultaneously on the same dataset, enabling continuous data flow through the graph.

16. What do you mean by Sort Component in Ab Initio?

Ans: The Sort Component in Ab Initio is a critical tool for organizing data sequences. It operates based on two parameters:

• Key: Determines the order of data sorting.
• Max-core: Dictates the frequency at which data is moved from memory to disk during the sorting process.

17. What does the dedup component and replicate component do?

Ans: 

Dedup component - It is used to remove duplicate records from the flow based on a specified key.

• Replicate component - It is used to combine input records from multiple sources into one flow and write a copy of that flow to output ports.

18. What are the types of partition components in Ab Initio?

Ans: Ab Initio offers several partition components, each serving a specific data distribution purpose:

• Partition by Round-Robin: Distributes data evenly in block-size chunks.
• Partition by Range: Splits data based on a set of ranges and a key.
• Partition by Key: Divides data according to a specific key.
• Partition by Percentage: Allocates data proportionally to fractions of 100.
• Partition by Expression: Segregates data based on a DML expression.
• Partition by Load Balance: Distributes data dynamically for load balancing.

19. What is a surrogate key?

Ans: A surrogate key in Ab Initio and other database systems is a unique, system-generated sequential number, often used as a primary key. It is particularly useful for maintaining data integrity and facilitating easier joins and queries.

20. Explain about the sandbox.

Ans: In Ab Initio, a sandbox refers to a user-specific workspace or directory that contains a collection of graphs and related files. It's essentially a local version of a project housed in the EME, useful for version control, development testing, and easy navigation between different project components.

21. What is the relation between limit and ramp?

Ans: In Ab Initio, 'limit' and 'ramp' are parameters used to define a graph's reject tolerance. 'Limit' specifies the maximum number of allowable rejects, while 'ramp' sets the rate of rejection. The formula for calculating reject tolerance is: limit + (ramp * number_of_records_processed).

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22. How will you handle it if DML is changing dynamically?

Ans: Handling dynamic DML changes in Ab Initio can be approached in various ways:

Utilize conditional DML to adjust dynamically.

Apply vector functionality when invoking DMLs.

Employ the MULTI REFORMAT component to manage different DML structures.

23. What are the air commands used in Ab Initio?

Ans: Ab Initio includes several 'air' commands for project and object management, such as:

air object ls: Lists objects.

• air object rm: Removes objects.
• air project modify: Modifies project settings.
• air object versions -verbose: Displays detailed version information.
• air lock show -user: Shows user lock status.
• air sandbox status: Provides the status of the current sandbox.

24. What are the types of output formats that we can get after processing data?

Ans: After processing data in Ab Initio, outputs can be generated in various formats, including:

• Charts.
• Tables.
• Vectors.
• Plain text files.
• Maps.

25. Explain about the rollup component.

Ans: The rollup component in Ab Initio groups records based on specific field values. It employs a multi-stage transform function with stages like initialize, rollup, and finalize to aggregate data effectively.

26. What are is_valid and is_define used for?

27. How does the force_error function work?

Ans: The force_error function in Ab Initio is used to enforce error conditions. If specified conditions are not met, it triggers an error, halting graph execution. It directs erroneous records to the reject port and sends error messages to the error port.

28. How to improve the performance of a graph?

Ans: Enhancing the performance of an Ab Initio graph can be achieved through various methods:

• Prefer lookups over joins and merges for efficiency.
• Use union functions instead of duplicate removers when joining files without requiring duplicates.
• Minimize the use of sort components.
• Limit the use of regular expression functions in transform functions.
• Avoid using the broadcast partitioner for large datasets.
• Focus on using only necessary fields in sort, reformat, and join components.

29. List the commonly used components in an Ab Initio graph?

Ans: Common components in an Ab Initio graph include:

• Input/Output File Components.
• Lookup File Components.
• Input/Output Table Components.
• Join Components.
• Sort Components.
• Partition Components.
• Gather Components.
• Reformat Components.
• Concatenate Components.

30. Explain the difference between conventional loading and direct loading.

Ans: 

Conventional Loading: Involves checking all table constraints against the data before loading it.

• Direct Loading: Disables table constraints initially, loading data directly for speed. Post-loading, constraints are checked against the new data.

Conclusion

Major companies like American Express, Citi Bank, JP Morgan Chase, Time Warner Cable, Home Depot, Premier, etc., use Ab Initio for their data processing and integration needs. The customers include 20% of Computer Software, 10% of Information Technology and Services, 9% of Higher Education, 9% of Education Management, etc. It has a market share of 5.12%. The Ab Initio developer and admin job posts are very high in demand. So, prepare well on the basics of Ab Initio, and you will have a high chance of cracking the interview.