RomVault's directory settings allow you to specify the merge type of your sets if parent/clone information is available in the DAT. This is most common with MAME and HBMAME “listxml” DATs.
A non-merged set contains absolutely everything necessary for a given game to run packaged in a single folder or archive. Every game is completely independent from any other game.
A non-merged set is ideal for those who only want to use specific games on their PC, Raspberry Pi, etc. Since all games are self-contained, there is no need to search for the dependent parent files, BIOS files, and device files.
Even though non-merged games normally do not include BIOS or DEVICE files within the game, RomVaut does include these within the game's set. This ensures that every single game can be copied and ran independently without the need for any extra files.
A split set is one where the parent set contains all of the normal data it should, and the clone sets contain only what has changed as compared to the parent set. This saves some space, but isn’t quite as efficient as a merged set. The clone sets can't operate without their parent set.
The parent and clones in split sets do not include BIOS or DEVICE files - they are separate files within the set. This is per MAME design. For example: 100lions.zip, which has no BIOS in the parent; and galaga.zip, which has no device files in the parent.
A merged set takes the parent set and its clone sets and puts them all inside the parent set's folder or archive. Using Pac-Man as an example: A merged set takes the Puckman, Midway Pac-Man (USA) sets, along with various bootleg versions, and combines it all into puckman.zip (the parent's archive).
The parent games in a merged set do not include BIOS or DEVICE files - they are separate files within the set. This is per MAME design. For example: 100lions.zip, which has no BIOS in the parent; and galaga.zip, which has no device files in the parent.