Optimized QVD load

QVD ( QlikView Data) file is a powerful feature of QlikView. QVD is a native QlikView format. It can be only written or read from 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.

Few advantages of using QVD files include:

• faster load times
• Less overhead on Database servers and networks
• Portability across QlikView applications
• Incremental Load

Now, lets look into optimized QVD loads. Optimized QVD loads are muck quicker than non-optimized ones. During optimized QVD load, the data is directly sent from disk to RAM memory in the same format. Optimized QVD load is one of the important step in optimizing QVW reload performance.

Optimized mode can be utilized only when all loaded fields are read without any transformations , though the renaming of fields is allowed. A WHERE clause causing QlikView to unpack the records will also disable the optimized load. However, simple Exists() function on a single field is allowed.

Some of the operations that can make QVD load non-optimized are

• Join 
• Mapping load 
• Derivations / calculated fields 
• Where clause

Things that are allowed in optimized QVD load are

• Renaming the fields 
• simple exist() function on single field to filter the records 

Optimized QVD load is indicated in Script Execution Progress window. "qvd optimized" text is displayed whenever QlikView uses optimized QVD load to read the QVD file. However, "qvd optimized" text does not appear in log files.