.QVD vs .QVW

[#1]

.QVDs are QV data files and used as an intermediate file. for example, instead of reading from oracle and excel every time we load them into .QVD and that will make them run faster.

is it correct that we use this .QVD as input data for report?

Now, .QVW are application files which may or may not necessarily contain (data used in report, sheet objects, scripts and macros etc.)

Question is: Since .QVW also has the data used in report is it OK to delete .QVD? (I am not even sure if this question is legitimate)

Why have same data used in two different files?

Or, .QVDs deleted by it self after you have .QVW ready.

[johnw · Accepted solution]

QVDs are generally used when you have more than one application that needs the same data. It is then more efficient to read it from your source once rather than several times. But if you only have a single QVW using that QVD, there aren't many reasons to go through the extra step of creating the QVD. Just read the data directly in your application.

[#3]

Of course a very good reason to use a QVD even for a single document is when that data is static, such as historical invoice data. Reloading a QVD is MUCH faster than other data sources.

Many people will use a partial reload instead so that only new data is loaded though, but this technique can mean a document loads as quickly with a full reload compared to a partial. Some of our processes use FTP'd data that can fail 'quietly' causing all sorts of issues with partial reloads - full reload can be much more resilient.

Regards,

Gordon

[#4]

What compression rate are we looking at when using .QVD? for example, I have 2 GB of oracle data and mostly its static. Ofcourse it will be beneficial to use .QVD in this case, if I am getting this whole thing right.

what will be the new reduced size of .QVD or .QVW with oracle data of 2GB? I heard in one of the tutorial that it can be compressed almost 85%. Is that true?

I cant try it myself because I dont have that huge DB and I have very basic QV application from QV's website.

[rwunderlich]

The size of the QVD is mostly affected by the cardinality -- the number of unique values -- of the data. So size will vary dependent on the actual data contents. But 85% is not uncommon.

-Rob