1 Reply Latest reply: Jul 17, 2015 11:25 AM by Andrew Whitfield RSS

    Extension .qvd

    Fabio Mazzarelli

      Immagine.pngI'm looking at the examples included in the program and use of files known .qvd . What you are or how you carry ?

        • Re: Extension .qvd
          Andrew Whitfield

          Hi Fabio,

           

          this is from the Qlikview Reference Manual:

           

           

           

          QVD Files

          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 optimized (faster). The selected mode is determined

          automatically by the QlikView script engine. Optimized mode can be utilized only when all loaded fields

          are read without any transformations (formulas acting upon the fields), though the renaming of fields is

          allowed. A WHERE clause causing QlikView to unpack the records will also disable the optimized load.

          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.

          28.1 Purpose of QVD Files

          QVD files can be used for many purposes. At least four major uses can be easily identified. More than one

          may apply in any given situation:

          Increasing Load Speed

          By buffering non-changing or slowly changing blocks of input data in QVD files, script execution becomes

          considerably faster for large data sets.

          Decreasing Load on Database Servers

          The amount of data fetched from external data sources can also be greatly reduced. This reduces work load

          on external databases and network traffic. Furthermore, when several QlikView scripts share the same data it

          is only necessary to load it once from the source database into a QVD file. The other applications can make

          use of the same data via this QVD file.

          Consolidating Data from Multiple QlikView Applications

          With the Binary (page 225) script statement it is possible to load data from only one single QlikView application

          into another one, but with QVD files a QlikView script can combine data from any number of Qlik-

          View applications. This opens up possibilities e.g. for applications consolidating similar data from different

          business units etc.

          Incremental Load

          In many common cases the QVD functionality can be used for facilitating incremental load,

           

          HTH - Andy