Can qvw replace qvd?

[#1]

Hi,

I load my data into qvw file with 170M. And the same data save as qvd file with 260M.

I can load data from both qvw and qvd. And I think it is the same speed.

Can qvw replace qvd? [:D]

[erichshiino]

To load data from a QVw you need to use the binary command.

Using this you are able to load only one QVW.

On the other hand, you can load as many qvds as you want in one script

[#3]

🙂 Is this the only different?

qvw file is smaller then qvd file, isn't it?

[erichshiino · Accepted solution]

Each QVD has only one table.

When you use binary you can load the whole model (including section access)

QVW has data compression, you can disable it on document properties (default is high compression)

[marcohadiyanto]

hi,

of course qvw file is smaller then qvd file.

you want use qvw as your data source? binary load can only use once times.

so we can't add another qvw as data source..

[rwunderlich]

qvw files may appear smaller than qvd files because qvw file may be stored compressed, qvd is stored uncompressed. A qvd contains a single table. qvws can contain multiple tables. For more information see:

http://qlikviewnotes.blogspot.com/2011/02/qvd-questions-and-answers.html
http://qlikviewnotes.blogspot.com/2011/03/qlikview-compression.html

[#7]

Hi Rob,

I have a query in Compression from the post in the url http://qlikviewnotes.blogspot.com/2011/03/qlikview-compression.html

If you are trying to get a document to load faster, try turning off document compression and benchmark your results. Consider the type of disk when making this decision. Compression may more important in a network storage environment where reducing the amount of data transferred is a significant performance factor.

Do you mean because of compression there will be an performance issue?

[#8]

Wormecota,

You can use QVW instead of QVD .

In qvd data is smaller (1 Table) but QVW has huge data model(Data) in it.

So that will depend on your requirement But u can use QVW by using Binary Load in script

Binary relaod will be call in the very first line of your new script.

Regards,

Dushyant

[suniljain]

QVW is just like EXE.

[rwunderlich]

XXX wrote:
Do you mean because of compression there will be an performance issue?

The elaplsed time to load a document and make it ready for the user is the sum of read I/O time and time to perform de-compression. Chart calc time should be unaffected by document compression and is not relevant to this question (I won't be surprised if someone corrects me on this).

If a qvw is compressed, a certain amount of CPU, and therefore elapsed time, will be spent in performing the de-compression. The elapsed time impact will depend on processor availability and the degree of de-compression required. My testing with files loaded from local disk is that in most cases, an uncompressed file will load faster. That is, the overhead of doing de-compression is more than the addtional read I/O time of reading a larger, uncompressed file.

A compressed file is smaller and therefore will require less data to be transferred over the I/O channel. If the I/O channel is relativley slow, such a networked disk, the scales may tip the other way. The total elapsed time for loading a compressed file over a network link may be better due to moving less data over the slower connection.