USB-Discs, the cloud and portability
One of the main goals in the development of Nemp was portability. Nemp should not have to be installed, but should run just like that - including the media library. Even if Nemp is located with the entire music collection on an external hard drive, and when the drive is connected, the entire data is sometimes on D:\ and sometimes on E:\. So Nemp should be portable in the literal sense.
Whether Nemp should behave as portable software or as "installed" is controlled by the file UseLocalData.cfg in the Nemp directory (see first chapter Installation).
In the years since the first Nemp version, another scenario for "portable software" has become relevant: The use in online drives, which are often synchronized in a specific directory of a computer. Since version 4.14 Nemp is also prepared for this case: If Nemp is located in such a directory together with all music files, then it works on all computers - no matter what the directory on the respective computer may be.
For the first case - the use on external drives - not only the paths to the individual music files are stored in the media library, but additionally information about the drives on which the data are located. Nemp examines the drives on startup and corrects the path information if necessary.
This also works while Nemp is running. For example, if you forgot to connect the external hard drive with your music collection before starting Nemp, it doesn't matter. As soon as it is connected, Nemp registers this and automatically adjusts the paths during operation.
For the second case - the cloud drives - Nemp stores only relative paths in the media library. These are completed appropriately at startup or when loading the media library. However, this only works as long as only one drive is used for the media library. As soon as several drives or partitions are in play, relative paths are of no use anymore.
Both variants usually work very well, and do not interfere with each other. In some cases, however, these automatic correction methods can have undesirable side effects. In the first case, for example, two identical backups of the music collection on two different drives are recognized as "different". And in case of relative paths, the file with the media library cannot be moved arbitrarily. Its position relative to the music files must remain the same.
Therefore, both variants can be turned on or off in Settings→General Settings→Nemp portable.