SQL Server Integration Services, commonly known as SSIS, is a crucial component of the Microsoft SQL Server 2005 capable of performing a wide variety of data migration tasks. It serves as a platform for developing corporate-level data transformation and data integration solutions.
People use it as an efficient data warehousing tool, capable of handling data extraction, data transformation, and data loading (ETL). It is capable of extracting data from multiple sources, such as Excel files, SQL Server databases, and elsewhere. Also, SSIS makes it easier to migrate data stored in one database to another. You can use SSIS for automating SQL Server maintenance and the updation of multidimensional cube data.
If you are recently trying to prepare for interviews focused on SSIS, this article will help you get a better understanding of the technology. We have summed up the top frequently asked SSIS interview questions and answers here. These will help you be prepared to ace your interview and impress your potential employer.
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Top SSIS Interview Questions and Answers
1. What is SSIS?
SSIS stands for “SQL Server Integration Services,” introduced by Microsoft as a component of the Microsoft SQL Server database. It is capable of performing an array of data migration tasks. Also, it serves as a data warehousing tool for ETL (extract, transform, and load) operations.
SSIS comes with a rich set of built-in tasks and transformations tools for constructing packages. There are two ways to create an SSIS package; one is programmatically or via GUI that helps the user create a package without writing a single line of code.
The primary objective of SSIS is to make the process of data migration, manipulation, and transformation easy and effortless. This tool has the power to define the workflow of process and ask; users can easily determine how the process should work and perform various tasks.
2. What are the advantages of SSIS?
The following are the advantages of using SSIS:
- SSIS is capable of handling the data from heterogeneous data sources in the same package
- Works with complex data, such as FTP, HTTP, MSMQ, analysis services, etc.
- Offers transformation functionality and is easier to maintain
- Tight integration with Microsoft Visual Studio and SQL Server
- Helps remove the network as a bottleneck for the insertion of data by SSIS into SQL
- Good at performing complex transformations, structured exception-handling, multi-step operations, and aggregating data from several data sources.
- Allows the loading of data in parallel across multiple destinations
3. What are the disadvantages of SSIS?
The following are the disadvantages of using SSIS.
- For checking the package execution reports, you will require Management Studio rather than it being published to reporting services
- You may encounter an issue or find it challenging to run multiple packages simultaneously. This is because SSIS uses a large amount of memory usage and conflicts with SQL.
- It is also challenging to allocate CPU resources while running several packages in parallel. You need to make sure that it is divided between SQL and SSIS properly as the SQL will be considered first, which makes SSIS run very slow.
4. What are the critical features of SSIS?
The following are some of the most important features of SSIS:
- Improves data quality by providing data cleansing and profiling
- Helps in smooth data integration from several data sources
- Easy integration with other components of Microsoft SQL products
- Enriched studio environment and graphical tools
- Offers workflow functionalities such as file transfer protocol
- Provides the APIs for SSIS object modeling
- Implements high-speed data connectivity efficiently
- Comes with packaged data source connectors
- Organizes data mining query and lookup transformation
5. Why use SSIS?
The following are some significant reasons to use SSIS:
- SSIS helps merge the data from several data stores and load data to various destinations while ensuring great speed
- Very versatile and flexible, reducing the need for dedicated developers
- Tightly integrates with the Microsoft family of products
- Cost-effective tool, offering robust error handling and a smart programming style that will help developers write lengthy code quickly
- Provides business intelligence output with the data transformation process
- Automates the process of data loading and other administrative operations
- Detailed documentation and strong community support
- This tool can analyze, clean, load, transform, aggregate, merge, and extract the data with ease.
- Easy to configure, manage and handle
6. When can you use SSIS?
You use SSIS:
- If you want to integrate and analyze the data from various sources
- Whenever you want to infuse business intelligence into the process of data transformation
- When you have to work with various business workflows where the information will be retrieved by passing the different sets of parameters
- When your project requires the analysis of the various data marts and data warehouses
- When you want to automate administrative tasks such as backup, restore, loading packages, etc.
- When you want to automate the maintenance of the SQL Server database
7. List all the tasks of the SSIS integration process.
The following is a list of SSIS integration tasks:
- Analysis Services Processing Task that processes one or more objects at a time
- Send Mail Task will send the emails with an output of the package workflows
- XML Task will work with XML files and merge multiple sources into a single file
- Execute Package/Process Task will execute the package from another package or break them into simpler packages
- Execute SQL Task will execute the SQL statements from a package
- Data Flow Task will perform the ETL of data from various sources
- FTP Task will upload and download the files with FTP
- Script Task will add the code for one or more tasks that are not a part of SSIS
8. What are the important components of the SSIS work environment?
The following are the major components of the SSIS work environment:
- SSIS Toolbox: Contains all the necessary operational tools for controlling the data flow
- Properties Window: Displays the properties of the selected component
- SSIS Package: Shows the exact package that is currently in use
- Solution Explorer: Determines the browsing of existing solutions and all the available files
- Connection Manager: Displays existing active connections
9. What are packages in SSIS?
In SSIS, packages are the collection of connections, data flow elements, parameters, control flow elements, event handlers, variables, and configurations. There are two ways to assemble all these components in an SSIS package, and this can be done either by SSIS’s graphics design tool or by writing a program.
Every SSIS package has a control flow and data flow. All other elements, like variables, parameters, event handles, configurations, are optional.
You can use the packages to populate the data from various sources that are finally used to carry out administrative tasks. These packages are created in a business intelligence development studio.
10. What are SSIS expressions?
In SSIS, expressions are mainly used for filtering the necessary information depending on various conditions. You can use the expression in conjunction with loops, conditions, and dynamic connections.
These expressions consist of symbols, literals, identifiers, etc. You can also use them to update the properties at the runtime. You need the expression evaluator for parsing the expression that will validate the rules of the expression.
11. What is a manifest file?
This file is a utility that stores the information required for deploying the packages with the help of a file system wizard and SQL server database.
12. Explain data transformation in SSIS.
Data transformation is a process that will extract the desired data from various data sources, called data extraction. After extraction, the data is managed and transferred to a specific location. The transfer of the data to multiple locations is based on predefined rules.
The transformations are of various types such as:
- Business intelligence transformation
- Row transformation
- Split and join transformation
- Rowset transformation
- Auditing transformation
- Custom transformation
13. Describe the SSIS catalog.
SSIS catalog is a database that securely stores all the deployed packages and controls them efficiently. You can deploy your packages in the SSIS catalog, and each package will be stored in the catalog as a centralized database.
14. What are SSIS containers?
SSIS containers are objects that provide the functionality to the structure and tasks of the SSIS package’s control flow. These containers loop through all the task sets until they are logically grouped or meet the specific criteria. You can even nest these containers. These containers are set within the package designer section under the Control flow tab.
15. What is the SSIS checkpoint?
SSIS checkpoint is a property ensuring that the user will get the point of restart from the failure point. If you set this checkpoint property to true, a checkpoint file is created containing all the necessary information on how to run the package from the failure point.
If the package runs successfully, the file will get deleted and created again when the package runs. This is useful if you want to avoid the re-running of the entire project in case of failure.
16. What is the precedence constraint?
The precedence constraint helps determine the sequence and logical order of tasks present in the SSIS package in which they should be implemented. It acts as the connector that connects all tasks.
17. What are SSIS connection managers?
Connection managers are responsible for configuring a connection between an SSIS package and all other external heterogeneous sources from where the data is collected. It includes the necessary information such as the server, data sources, authentication details, and others.
18. Why are SSIS packages preferred over stored procedures?
There are several reasons for preferring SSIS packages over stored procedures, as explained below:
- SSIS is capable of handling complex transformation processes involving slow-changing dimensions
- It manages memory efficiently, and thus, shows better performance as compared to the stored procedures.
- SSIS has a GUI allowing developers to create complex transformations easily
19. What are conditional split transformations?
These transformations work similarly to the IF-ELSE condition that checks if the specific condition is true and then executes the given code. With the split transformation, you can also specify the order for the execution for various conditions and then provide the default value as the output.
20. Explain the error handling process in SSIS.
There is always a probability of an error while transferring vast amounts of data from various data sources to their destination. Therefore, it becomes necessary to identify the data that cause errors. To find the error, you must log the errors.
Each component of SSIS (source, transformation, and destination) should have log support using a secondary pipe that will define the behavior during errors. You can connect the error flow to another transformation as per the requirement. You can include the details such as the error column, error description, and codes in your error log for better understanding.
21. How do you create deployment utilities in SSIS?
In SSIS, a deployment is a process to update the package state from development mode to executable mode. You can deploy by right-clicking the operations on the integration services project and then selecting the build option. This will create the “package. dtsc” file under the bin folder. You can use the deployment utility for deploying the packages at the SQL server.
You can follow these steps for creating a deployment utility:
- Navigate to Project and right-click on it
- Double click on the properties option
- You can choose the path for your deployment by selecting the box next to “True” available under the Create Deployment Utility
- Close the window after saving all the changes
- Right-click again on the project and then click the build option. A deployment folder will be created under the BIN folder.
- Find the .manifest file in the deployment folder
- To perform the package deployment on the SQL server, double-click the manifest file and choose the deploy option
22. What are merge and union all transformations?
Merge transformations: This merges the data from two sources and creates a single output. You can use these transformations to break the data flow path and create a different error path. After the error is handled, you can merge it back to the main data flow. For implementing this sort, you need to sort the data, and the metadata should be the same for two different paths.
Union all transformations: This works similar to merge transformation but the only difference is that you do not have to sort the data. It will merge the data from different sources into a single output.
23. What are the different types of SSIS containers?
The different types of SSIS containers are as follows:
- Task host containers
- Sequence containers
- For loop containers
- Foreach containers
24. What is the task host container?
The task host container is the default container that stores a single task. In SSIS Designer, you cannot configure the task host separately; but you can set the properties of the task it stores within. With this container, you can extend the variables and event handlers to the task level. This container will empower the task to use the features of containers.
25. What is the sequence container?
Using a sequence container, you can define the control flow as the subset of the package control flow. These containers will group the packages into several control flows containing one or more tasks and containers.
You can include many tasks along with containers in the sequence container that are displayed in the Control Flow tab. Also, you can drag and drop containers from the toolbox under the design pane and then add a set of tasks into the container.
You can achieve the following things using sequence containers:
- Group specific tasks to disable a portion of the unused package
- Narrow the variable scope to the container level
- Manage the properties of the task by setting container properties
- Ensure multiple executions of tasks by making use of one method
- Create data-related tasks and transactions but not packages as a whole
- Create event handlers such as sending mail
26. What is the for loop container?
The loop container is useful for defining the repeating control flow within a package. The for loop works similarly to the for loop structure of any programming language. In the case of the for loop container, it will evaluate an expression and then repeat the specific part of the code until the expression evaluates to false.
This container uses the following elements to define the loop:
- An optional initialization expression that assigns values to the loop counters
- An evaluation expression, which will be evaluated to test whether the loop should continue or not
- An optional iteration expression that changes the loop counter value
27. What is the ‘for each’ container?
The ‘for each’ loop container has a powerful loop mechanism that enables looping using object collection. It defines a repeating control flow in an SSIS package. The implementation of ‘for each’ loop container in SSIS is analogous to for loop in other programming languages. It uses a ‘for each’ enumerator to enable the looping in an SSIS package.
28. What are the various types of lookup cache modes in SSIS?
The following are the various types of lookup cache available in SSIS:
- Full cache mode: In this mode, you can query the database before executing the data-flow task. It is one of the critical parts of the pre-execution of the data-flow task. In this mode, the complete data of the table will get copied to the lookup cache of SSIS.
- Partial cache mode: in this mode, you can query the new rows of the database from different data sources. The matched data will be cached to the SSIS lookup cache. If the lookup cache is full, previously stored data will be removed depending on the usage statistics and make space for the newly matched rows.
- No caching mode: The data will not be cached unless matched rows exist from two subsequent sources. You can run queries on the database to get the matched data.
29. What is logging of the SSIS execution?
SSIS comes with the logging process that will allow the system to analyze and write the logs for every run-time event. It can be used for logging the custom messages that need to be enabled manually by developers.
In SSIS, we work with various data sources; thus, it is necessary that the logging is supported in multiple formats such as text files, XML, etc. these logs are maintained at the package level, meaning whenever a package executes the task, it will get logged to other package logs.
30. Is it possible to schedule packages?
Yes, you can schedule packages for any time as required. You can do it by designing SQL Server agent jobs with similar work steps as the SSIS packages. This job will fetch the ‘dtexec’ order utility for executing the bundle. You can run this bundle or schedule it as per the request.
31. What is the config file in SSIS?
The config file provides the inputs to the connection manager regarding the properties used by the packages/tasks during run-time. It is useful when we have to deploy the changes to multiple servers without worrying about the configurations of the packages. The config files will be automatically picked based on the server. You can store the config properties in various ways, as described below:
- XML configuration file: Data is stored as an XML file
- Environment variables: The config data is stored as part of environment variables
- Registry entry: The config is stored in the registry
- Parent package variable: The config is stored as a variable in a package of a task
- SQL Server: The config is stored in a database table on the SQL Server
32. How can you add a recordset variable in the Script task?
You can use variables in the script tasks for exchanging the data with other objects of the packages. The script task uses the property “variables of Dts object” to read and write the variables object of the package. For making the variable available to the custom script, you can add them to the read-only or read-write variables list. These variables are case-sensitive, so make sure that you add the right variable name to the list.
33. What is SSIS breakpoint?
In SSIS, a breakpoint is a property, allowing the developers to pause the execution of the package in the BI system. It is a stopping point at any state that enables the developers to review the status of the variables, data, or the entire package.
34. What are the steps for applying or removing breakpoints?
All the breakpoints in SSIS are configured in BIDS, and you can follow the steps below to apply or remove the breakpoints in SSIS.
- First, go to the control flow interface under the BIDS
- Right-click on the object where we want to apply/remove the breakpoint
- Click on the 'edit breakpoint' option
- Then, you can set the breakpoint or disable it as per your requirement
35. How does an error occur? Mention some critical errors in SSIS.
There could be various reasons for an error, such as unexpected data input, applying data transformation, loading data to destinations, and many others.
The following are the most critical errors encountered in SSIS:
- Data connection error: It occurs when you cannot initialize the connection manager with a connection string. This error can occur either at the source or destination.
- Data transformation error: It may occur during the transfer of data from the source to the destination
- Expression evaluation error: It occurs at the run-time while evaluating the values
36. What is data profiling in SSIS?
It is the process of analyzing the state of the source data to obtain a proper understanding of data cleaning, pattern identification, etc. This process is generally carried out at the initial stage of project development, ensuring that it will support the destination design schema. Also, it will enable you to understand whether the data is ready to use, and where to use it, in the current development cycle.
37. What is the ignore failure option in SSIS?
The ignore function in SSIS is generally used for ignoring the errors during the transformation process. While transforming, the error will get ignored, and the data row will be iterated to move to the next transformation. This function is useful when we need to deal with incorrect data coming from the source. Using this option, only valid data will get moved to the destination, and invalid data will be moved to a separate file.
38. What are different event logging mode properties in SSIS?
Every task and package has a property “Logging mode” that accepts the following three options:
- Enabled: Use this option to log the components
- Disabled: Use this option to disable the components
- UserParentSetting: Use this option to modify or optimize the parent's settings
39. Can we stop a forever-running package in SSIS? If yes, how?
Yes, you can stop a forever-running package, but it depends on where the package is running. If the package is running within the SQL Agent, you can kill the entire process using T-SQL. But if the package is running within the SSIS catalog, you need to use the stop-operation method. Apart from this, you can use the Active operations window to stop the SSIS catalog’s running process.
40. What are the different file formats and connections that are supported by SSIS?
The following are the different file formats and connections that are supported by SSIS:
- Flat File
- .net SQLClient
41. How do you deploy an SSIS package on production?
For deploying the SSIS package, you will require a manifest file that can be run either on the file system or SQL server.
42. What are the components of data flow in SSIS?
The three data flow components are:
43. What is the OLE DB command transform?
In SSIS, the OLE DB command transform is used to execute the SQL statement for each row in an input stream. It is analogous to an ADO command where the object will be created, prepared, and executed for each row of a result set. Then the data will be provided for parameters that you can set in the SQL statement.
44. Why is the bulk insert task used in SSIS?
You can use the bulk insert task for uploading a large amount of data from the flat files into the SQL server. This task will only support the OLE DB connections for the destination database.
45. What are the different types of data viewers in SSIS?
The following are the different data viewers available in SSIS:
- Scatter Plot
- Column Chart
46. What are the possible locations for saving the SSIS package?
The following are possible locations:
- SQL Server.
- Package Store
- File System
47. How do you notify the team about the package failure?
There are two ways to notify the team about the package failure using two ways. One is adding a Send Mail Task in the event handlers of the SSIS Package, and the second is setting the notification in the SQL agent whenever the package runs.
48. What are some best practices when using SSIS?
The following are some best practices for using SSIS:
- Make sure to avoid performing logged operations
- Make a clear plan for efficiently utilizing the resource
- Optimize the data source, lookup transformation, and destination
49. What is the role of the event handlers tab in SSIS?
With the help of the event handlers tab, you can configure workflows for responding to the package events.
50. How do you perform an incremental load?
You can perform the incremental load using the Timestamp column available in the source table and then store the last ETL timestamp.
These SSIS Interview Questions Should Prepare You Well
SSIS is a crucial component of Microsoft SQL Server and an essential element of the Business Intelligence suite. The principal goal of SSIS is to resolve issues encountered in workflow applications and data integration.
Many users consider SSIS one of the top ETL tools in the market and the best buddy for skilled SQL developers. SSIS is suitable for developers dealing with huge and complex data volumes. The developers commonly use Visual Studio for writing complex codes, ensuring a big margin for errors.
If you are about to appear for an interview that is SSIS related, this article can serve as excellent preparation.
To start getting familiarity with SSIS integration with SQL, We recommend you to start with this course:
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