INTERVIEW QUESTIONS DATA WAREHOUSING DATASTAGE DETAILS

Question: What is the difference between sequential file and a dataset? When to use the copy stage?

Answer: Sequentiial Stage stores small amount of the data with any extension in order to acces the file where as DataSet is used to store Huge amount of the data and it opens only with an extension (.ds ) .The Copy stage copies a single input data set to a number of output datasets. Each record of the input data set is copied to every output data set.Records can be copied without modification or you can drop or change theorder of columns.

Sequentiial Stage stores small amount of the data with any extension in order to acces the file where as DataSet is used to store Huge amount of the data and it opens only with an extension (.ds ) .The Copy stage copies a single input data set to a number of output datasets. Each record of the input data set is copied to every output data set.Records can be copied without modification or you can drop or change theorder of columns. Source: CoolInterview.com

Seq file : u can view the data in Unix box or View data button.
U can delete the file in unix like rm file name

DataSet : U can't see the data in dataset stage. even cant see the data in unix box also
But if u want to delete the data u can use $orchadmin < delete | del | rm > [-f | -x] descriptorfiles…. Source: CoolInterview.com

seq file::1.extract/load from/to seq file.max==2GB.
2.when used as a source at the time of compilation it will be converted into native format from ASCII.
3.By default it will be processed in sequence only.
4.doesn't support null values.
5.processed at the server.
6.supports .csv,.txt,.xls etc...

data set::1.used as an intermediate stage.
2.at compile time conversion is not required.
3.datasets get processed in our local system.so performance is improved as the server is not loaded.
4.supports only .ds
5. 2GB limit is not thete
Source: CoolInterview.com

seq file::1.extract/load from/to seq file.max==2GB.
2.when used as a source at the time of compilation it will be converted into native format from ASCII.
3.By default it will be processed in sequence only.
4.doesn't support null values.
5.processed at the server.
6.supports .csv,.txt,.xls etc...

data set::1.used as an intermediate stage.
2.at compile time conversion is not required.
3.datasets get processed in our local system.so performance is improved as the server is not loaded.
4.supports only .ds
5. 2GB limit is not thete



Source: CoolInterview.com

sequential file is used to extract the flat files like(.txt,csv)files and load into the target.
It doesnot support null values.
It is used when data is >=2GB only.(if data is >2GB we go for file set)

DATASET:it is used as intermediate stage.
It supports when data is >2GB.
It can understand Archastrate Engine language.
It supports parallelism.
Its extension is .DS
It can be used as source and target .... Source: CoolInterview.com

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