Virtual Variables: Manage Virtual Variables
The Manage Virtual Variable dialog allows the user to recreate Virtual Variables that are no longer available due to the FastStats system being rebuilt. The user can also permanently remove virtual variables (or old virtual variable definitions) that are no longer needed.
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Most Virtual Variables will be created not by the administrator in FastStats Designer but by end users in FastStats. When the FastStats system is rebuilt using Designer it won't necessarily include the definitions for recreating the Virtual Variables and they will become unavailable to the user.
From the File - Tools menu select Manage Virtual Variables...
In the above image you can see that the description of the variable is shown (if available) as well as the 8 character reference name. Variables can be refreshed in two ways, "By Rule" or "From URN Snapshot" (see below). Select which option you want for each variable to be refreshed and then press the "Refresh" button.
Refreshing a Virtual Variable "By Rule"
Whenever an action is performed on a Virtual Variable, such as creating it or modifying it the definition of the change is saved. These constitute a set of "rules" that are used to put the variable in its current state. When refreshing the Virtual Variable these rules can be rerun to recreate the Virtual Variable.
However, most of the rules used to recreate a variable will use selections on other variables. When the FastStats system is reloaded the data in the system will change and the selections may now select different records. For example, one code of a selector Virtual Variable can be set to a selection of people that bought a certain product. When the FastStats system is refreshed more purchases will have been added into the system and so more people will have bought the product in question. Therefore if the Virtual Variable is recreated "By Rule" the count for the particular code will go up as the selection now has more people in it.
Refreshing a Virtual Variable "From URN Snapshot"
If you create a Virtual Variable and want it to remain exactly the same after a rebuild of the FastStats system then you can optionally create a "URN Snapshot" of the variable. This takes the variable and records the value for each record against the Unique Reference Number (URN) for the table that the variable is on. Then when the variable is recreated from this snapshot it has exactly the same values as before.
This could be useful if the same PWE Model is created on a set of data after each rebuild of the FastStats system and you want to be able to compare how the model has changed between builds. When you create the PWE variable you are given the option to take a URN Snapshot of the variable. This can then be used to recreate the variable after the system rebuild.
A URN Snapshot can also be taken for any virtual variable at any time by right clicking on the variable in the System Explorer and selecting the "Create URN Snapshot" option.
Permanently Deleting Variable
Variables can also be permanently deleted using the Delete button. If the variable is not currently available in the system (indicated by a faded icon to the left of the description) then the information required to refresh the variable will be removed from the server. This will mean that the variable will no longer appear in the list of variables to be refreshed and it will never be able to be recreated.
If the variable is available in the system (indicated by a colour variable icon), then the variable will be deleted from the system and also permanently removed from the server.