The numeric identifier for the directory.
A value in the range 0 to 248 (DEFAULT = 0)
Every directory accessed by an application must have a unique DirId.
If you choose a DirId of 0, the internal ID of the directory is set to match the number assigned to the corresponding operating system file (i.e., ZIMnnnn where nnnn is typically a number between 0100 and 9999). Within each application, the internal ID of all application directories accessed at the same time must be unique.