How To Achieve Parallelism In Ssis?
Parallelism is achieved using MaxConcurrentExecutable property of the package. Its default is -1 and is calculated as number of processors + 2.
How Do You Do Incremental Load?
Fastest way to do incremental load is by using Timestamp column in source table and then storing last ETL timestamp, In ETL process pick all the rows having Timestamp greater than the stored Timestamp so as to pick only new and updated records.
How To Handle Late Arriving Dimension Or Early Arriving Facts.?
Late arriving dimensions sometime get unavoidable 'coz delay or error in Dimension ETL or may be due to logic of ETL. To handle Late Arriving facts, we can create dummy Dimension with natural/business key and keep rest of the attributes as null or default. And as soon as Actual dimension arrives, the dummy dimension is updated with Type 1 change. These are also known as Inferred Dimensions.
A transformation simply means bringing in the data in a desired format. For example you are pulling data from the source and want to ensure only distinct records are written to the destination, so duplicates are removed. Another example is if you have master/reference data and want to pull only related data from the source and hence you need some sort of lookup. There are around 30 transformation tasks available and this can be extended further with custom built tasks if needed.
How Can You Configure Your Ssis Package To Run In 32-bit Mode On 64-bit Machine When Using Some Data Providers Which Are Not Available On The 64-bit Platform?
In order to run an SSIS package in 32-bit mode the SSIS project property Run64BitRuntime needs to be set to "False". The default configuration for this property is "True". This configuration is an instruction to load the 32-bit runtime environment rather than 64-bit, and your packages will still run without any additional changes. The property can be found under SSIS Project Property Pages -> Configuration Properties -> Debugging.
How Is Ssis Runtime Engine Different From The Ssis Dataflow Pipeline Engine?
The SSIS Runtime Engine manages the workflow of the packages during runtime, which means its role is to execute the tasks in a defined sequence. As you know, you can define the sequence using precedence constraints. This engine is also responsible for providing support for event logging, breakpoints in the BIDS designer, package configuration, transactions and connections. The SSIS Runtime engine has been designed to support concurrent/parallel execution of tasks in the package.
The Dataflow Pipeline Engine is responsible for executing the data flow tasks of the package. It creates a dataflow pipeline by allocating in-memory structure for storing data in-transit. This means, the engine pulls data from source, stores it in memory, executes the required transformation in the data stored in memory and finally loads the data to the destination. Like the SSIS runtime engine, the Dataflow pipeline has been designed to do its work in parallel by creating multiple threads and enabling them to run multiple execution trees/units in parallel.
What Is A Task?
A task is very much like a method of any programming language which represents or carries out an individual unit of work. There are broadly two categories of tasks in SSIS, Control Flow tasks and Database Maintenance tasks. All Control Flow tasks are operational in nature except Data Flow tasks. Although there are around 30 control flow tasks which you can use in your package you can also develop your own custom tasks with your choice of .NET programming language.
What Is A Precedence Constraint And What Types Of Precedence Constraint Are There?
Parallelism is achieved using MaxConcurrentExecutable property of the package. Its default is -1 and is calculated as number of processors + 2.
How Do You Do Incremental Load?
Fastest way to do incremental load is by using Timestamp column in source table and then storing last ETL timestamp, In ETL process pick all the rows having Timestamp greater than the stored Timestamp so as to pick only new and updated records.
How To Handle Late Arriving Dimension Or Early Arriving Facts.?
Late arriving dimensions sometime get unavoidable 'coz delay or error in Dimension ETL or may be due to logic of ETL. To handle Late Arriving facts, we can create dummy Dimension with natural/business key and keep rest of the attributes as null or default. And as soon as Actual dimension arrives, the dummy dimension is updated with Type 1 change. These are also known as Inferred Dimensions.
What Is A Transformation?
A transformation simply means bringing in the data in a desired format. For example you are pulling data from the source and want to ensure only distinct records are written to the destination, so duplicates are removed. Another example is if you have master/reference data and want to pull only related data from the source and hence you need some sort of lookup. There are around 30 transformation tasks available and this can be extended further with custom built tasks if needed.
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| Wipro Frequently Asked SSIS Interview Questions Answers |
How Can You Configure Your Ssis Package To Run In 32-bit Mode On 64-bit Machine When Using Some Data Providers Which Are Not Available On The 64-bit Platform?
In order to run an SSIS package in 32-bit mode the SSIS project property Run64BitRuntime needs to be set to "False". The default configuration for this property is "True". This configuration is an instruction to load the 32-bit runtime environment rather than 64-bit, and your packages will still run without any additional changes. The property can be found under SSIS Project Property Pages -> Configuration Properties -> Debugging.
How Is Ssis Runtime Engine Different From The Ssis Dataflow Pipeline Engine?
The SSIS Runtime Engine manages the workflow of the packages during runtime, which means its role is to execute the tasks in a defined sequence. As you know, you can define the sequence using precedence constraints. This engine is also responsible for providing support for event logging, breakpoints in the BIDS designer, package configuration, transactions and connections. The SSIS Runtime engine has been designed to support concurrent/parallel execution of tasks in the package.
The Dataflow Pipeline Engine is responsible for executing the data flow tasks of the package. It creates a dataflow pipeline by allocating in-memory structure for storing data in-transit. This means, the engine pulls data from source, stores it in memory, executes the required transformation in the data stored in memory and finally loads the data to the destination. Like the SSIS runtime engine, the Dataflow pipeline has been designed to do its work in parallel by creating multiple threads and enabling them to run multiple execution trees/units in parallel.
What Is A Task?
A task is very much like a method of any programming language which represents or carries out an individual unit of work. There are broadly two categories of tasks in SSIS, Control Flow tasks and Database Maintenance tasks. All Control Flow tasks are operational in nature except Data Flow tasks. Although there are around 30 control flow tasks which you can use in your package you can also develop your own custom tasks with your choice of .NET programming language.
What Is A Precedence Constraint And What Types Of Precedence Constraint Are There?
SSIS allows you to place as many as tasks you want to be placed in control flow. You can connect all these tasks using connectors called Precedence Constraints. Precedence Constraints allow you to define the logical sequence of tasks in the order they should be executed. You can also specify a condition to be evaluated before the next task in the flow is executed.
These are the types of precedence constraints and the condition could be either a constraint, an expression or both Success (next task will be executed only when the last task completed successfully) or Failure (next task will be executed only when the last task failed) or Complete (next task will be executed no matter the last task was completed or failed).
What Is A Container And How Many Types Of Containers Are There?
A container is a logical grouping of tasks which allows you to manage the scope of the tasks together.
These are the types of containers in SSIS
Sequence Container - Used for grouping logically related tasks together
For Loop Container - Used when you want to have repeating flow in package
For Each Loop Container - Used for enumerating each object in a collection; for example a record set or a list of files.
Apart from the above mentioned containers, there is one more container called the Task Host Container which is not visible from the IDE, but every task is contained in it (the default container for all the tasks).
What Are Variables And What Is Variable Scope?
A variable is used to store values. There are basically two types of variables, System Variable (like ErrorCode, ErrorDescription, PackageName etc) whose values you can use but cannot change and User Variable which you create, assign values and read as needed. A variable can hold a value of the data type you have chosen when you defined the variable.
Variables can have a different scope depending on where it was defined. For example you can have package level variables which are accessible to all the tasks in the package and there could also be container level variables which are accessible only to those tasks that are within the container.
What Is An Ssis Proxy Account And Why Would You Create It?
When we try to execute an SSIS package from a SQL Server Agent Job it fails with the message "Non-SysAdmins have been denied permission to run DTS Execution job steps without a proxy account". This error message is generated if the account under which SQL Server Agent Service is running and the job owner is not a sysadmin on the instance or the job step is not set to run under a proxy account associated with the SSIS subsystem. Refer to this tip to learn more about it.
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