Reentrant VIs are used when you want to run several instances of the same VI simultaneously. When the聽VI is not reentrant, there is one data space for the VI. Therefore, only one caller at a time can be running the聽VI, and聽so a caller may have to "wait its turn" to use the VI.聽 This is the default option for a VI, but you can set a聽VI to be reentrant. There are two types of reentrancy: shared and preallocated.聽

If the VI you want to open multiple times is a top-level VI, you can duplicate the top-level聽VI on disk to a temp directory with a unique name and open the new file instance. It is not necessary to duplicate any SubVIs, only the top-level VI. You can then use the VI Server to open and run the copies.

LabVIEW code can run slowly if several of the same SubVI are聽used within the main VI and they are not聽Preallocated clone reentrant, this is聽because the SubVI's can only be accessed by one location at any given time hence resulting in the code slowing down.

You can make a multi-instance panel into a template VI, then open the file each time from the template. VI templates are VIs with the .vit extension. You can create a new VI from a template under聽File禄New禄Start from template. This creates a new instance of the VI, with its own memory space. These have distinct memory location when created and are just used as starting point for making another VI. You then need to configure whether that new created VI is or is not reentrant.聽

Dynamic VIs

You can open both VIs and聽VI templates with VI Server. VI Server is used to dynamically load and run a VI. With SubVIs, the code and the data space of the SubVI are loaded when the top-level聽VI is loaded. When you dynamically load a VI, instead of using it as a SubVI and loading it when the main program is called, its code will not be loaded until the SubVI is called by the VI Server. This saves memory at startup time.