IEC stores messages in hard drives, both temporary and permanently. If too many messages are stored in a single folder, performance will be negatively affected when IEC is reading and writing files. You must choose a suitable folder structure to prevent performance issues. Once the folder structure is chosen and IEC has processed messages then the folder structure cannot be changed without significant rework.
The messages are either stored in a tree-shaped folder structure or flat structure. The tree structure is the recommended structure. The other parameter that controls the folder structure is depth. That specifies how deep the tree should be. The structure is built up by creating folders based on the possible characters (16) and their positions in the UUID. That implies that the total number of folders that will be created is 16^depth.
The optimal file structure depends on the number of messages.
For example, given that the depth is set to 3 the UUID:
ea14ca5a-70d3-40a3-9adb-3bb93a507a09 will be located in the folder …\e\a\1.