How is qlikview able to handle Memory shrinking? Like suppose i am loading 5 qvd's each has about 50 MB but when i am converting it into qvw file the memory is very much less. How is qlikview able to handle this? I have a little knowledge that it is due to the data model that is created by us during qvw creation. But Anyother insights on this would be a lot more helpful.
QVD is a data format that can be read into qlik product very fast and that has no such algorithm of compression. Whereas, qvw is a compressed (Qlik's own algorithm) file, hence the file size is generally less than qvd.
The compression of a QVWfile can be set to high, medium or none on the document Properties | General tab. The compression happens when the document is saved (at the end if a reload task or by the user).
The QVD format is efficient because only unique values of the symbols are stored in the symbol table coupled with a memory efficient pointer structure, but it is not compressed. A QVD will often be larger than an equivalent xlsx spreadsheet (which is compressed), but much smaller than an equivalent CSV file.
Logic will get you from a to b. Imagination will take you everywhere. - A Einstein