What are QVD's and how can I use them

[#1]

Hello, newbie here.

Just started in a new job where they have purchased Qlikview. They've asked me to use the app and no one here can help me because the person who had my job is gone.

I understand the connections through odbc and direct table linking but one model here on the server is using many QVD files and I don't understand why. Through odbc I can connect to different tables direct in de database and replicate the QVW. My QVW file is much bigger though and therefore slower.

Can someone tell me what QVD's are and why someone want to use them instead of a direct link through odbc? How can I make a QVD?

Thx in advance

[#2]

From the HelpFiel:

"A QVD (QlikView Data) file is a file containing a table of data exported from QlikView. QVD is a native QlikView format and can only be written to and read by QlikView. The file format is optimized for speed when reading data from a QlikView script but it is still very compact. Reading data from a QVD file is typically 10-100 times faster than reading from other data sources. QVD files can be read in two modes, standard (fast) and super-fast. The selected mode is determined automatically by the QlikView script engine. Super-fast mode can be utilised only when all fields or a subset thereof are read without any transformations (formulas acting upon the fields), though the renaming of fields is allowed.

A QVD file holds exactly one data table and consists of three parts:

1) A well formed XML header (in UTF-8 char set) describing the fields in the table, the layout of the subsequent information and some other meta-data.

2) Symbol tables in a byte stuffed format.

3) Actual table data in a bit-stuffed format

"

.qvd is a propietary filetype that is optimized in many ways. You can save any temporary table in QV to a .qvd by using the STORE Command (STORE table1 INTO table1.qvd;)

Therefore you can encapsulate e.g the Data Staging from into a seperate QlikView File and then distribute or use the qvd. in many other Applications,

[#3]

qvd files are loaded much faster than other data sources, thus it is a good practice to have a qvw document used only to load the data into qvd files, and then to use those qvd as data sources for "real" documents

[#4]

Ok thx. I get it now!

[#5]

example :

TestTable:
LOAD number,
 label
FROM
[testdata.txt]
(txt, codepage is 1252, embedded labels, delimiter is '\t', msq);

STORE TestTable INTO [test.qvd]

[#6 · Accepted solution]

this example load data from a text file and stores it in a qvd :

TestTable:
LOAD number,
 label
FROM
[testdata.txt]
(txt, codepage is 1252, embedded labels, delimiter is '\t', msq);
STORE TestTable INTO [test.qvd]

[#7]

Yes, I understand. Thx very much!

[prabhu0505]

I have following questions in this thread:

1. In which situations, usage of QVD files may be unavoidable?

2. What is the reason behind 1 to 1 mapping between tabel and QVD?

3. Best Practices of QVD?

Anybody there.

Regards,
Prabhu

[#9]

A must read and watched:

http://community.qlik.com/blogs/qlikviewblogs/archive/2011/02/17/qvd-questions-and-answers.aspx