Practice Battles is a feature used in Riviera: The Promised Land to encourage the player to Skill Up. It is first available in Chapter 2's Lacrima Castle stage, and is effectively a level-grinding feature that the player can use at will. Note that Practice is not allowed within Elendia.
When going into Practice, depending on the version, the player can simply Change Enemy to something more preferable (GBA), or choose from a list of enemies (PSP); the latter of them being much more convenient than the former. The enemies that can be fought are among those encountered in the previous stage. While in Lacrima Castle, the player may only fight against Demon Shrub, Gatekeepers, and Wandering Beast. To begin, choose Start Practice. The player may also Cancel if they change their mind.
Once Practice has begun, selecting characters, items, and formation acts exactly the same as a real battle. Once in, the player may gain experience with any item they chose at their own pace, but once all enemies are defeated, the battle will end, with no ranking or Trigger Points awarded; an item can still be rewarded to the player at the end of the battle, based on the last-remaining enemy. You can also stop the battle at any time when you're done by opening the battle menu; an End option available only in this mode will end the battle as though all enemies were defeated. At the end of a battle, all characters will Skill Up with each item they filled the Experience Meter with, as usual. Also, usage of each item will not deplete their duration, making Practice Mode very handy; be wary of enemy skills that can decrease item uses, as they will still have that property regardless.
Finally, skills that transform items (Mix Potion/Elixir, Magical Cooking, Sterilize) can be used in Practice to transform the item without lowering its endurance. The changed item will not revert after the practice battle ends.