1. According to my understanding so far if there is a change in the source database fields, new QVDs are required..
Please let me know if my understanding is correct or explain otherwise.
2. Is it possible to update a QVDs from QVD? (This might be stupid question - sorry in advance :-))
If yes how? [As for as I know QVD can only be updated from QVW]
3. Is there any security involved on QVD level? For example, there are some QVDs are used for production reports (security has been implemented on these reports) in my company. Now some new fields have been added in the database which needs to be used in reports. If I just create new QVDs are rest every thing will remain the same, will it affect the security which is already in place?
1. Not always. It depends on the kind of change. If a date field is changed into a text field you can expect that some changes will be needed. If fields are renamed, you'll also need to change this in the load script. But you could rename the fields back to their old names in the script. That way the qvd would not change.
2. Yes, a qvd is simply a datasource. So you can load data from it, process it in some way and store the results in another qvd. A qvd is not an application, so you will need Qlikview to process the qvd's. There are other applications that can generate qvd's. Possibly they too can read one qvd, process the data and store that in another qvd.
3. Not as far as I know. qvd's simply store data, but are not secured in any other way than with file system permissions. The security is implemented in qvw documents and in the qlikview server configuration.
if their is a change in the database i.e when a field is added , you need not to add a new qvd, you can add the field at qvd only.
Upto my knowledge QVD only improves the performance of loading or they execute faster as in qlikview developer manual , qvd's are 100 times faster than normal excel files,text files,etc.
Thanks for your quick reply first of all, you are always very fast in replying (al least my questions) 🙂 (Is there a way to endorse you on this forum?? :-))
Here is what I understood from you answers, please confirm if my understanding is correct:
1. If new fields need to be added then QVDs needs to be updated (new QVDs needs to be created including those new fields)
2. We can always change QVD through QVW. Even if I just have a QVD then I need to create a QVW from it and then I can create a new QVD.
3. No security feature is involved on QVD level and if new QVD are used and rest is the same. Security will not affect.
