Savefiles are easy to use, but you should always plan what you’re going to save and what you don’t want to save. Use /tmp to avoid saving anything you don’t need, and you can avoid a lot of trouble.
In particular you should be careful that if you’re saving a player’s mob, you don’t accidentally save any other mobs. If you save a turf, you should avoid saving its contents unless you know there are no mobs standing on it (but usually it’s better to save x,y,z coordinates than the turf itself). This is explained further in the tmp vars entry.
Currently, overlays and underlays also save by combining each list into a single icon that saves its full icon data in the file. This may not be desired, so you can remove that data. Usually you’ll want to rebuild any overlay/underlay lists during Read().
A database file in DM is called a “savefile”. All of the contents of a savefile reside in a single file. The contents of the file are stored in database directories. These should not be confused with real directories in the external file system. The database directories are all contained inside the one file.
Each database directory contains a list of sub-directories and a buffer in which data may be written. The absolute path to a directory has the following format: “/Dir1/Dir2/…“. The current directory may be set by assigning its absolute path name to savefile.cd. A relative path (one that doesn’t begin with ”/”) may also be used, in which case the new path starts at the current directory. The path ”.” stands for the current directory, ”..” for its parent, ”../..” for its parent’s parent, etc.
A savefile may be created with new/savefile(name). The optional name argument may be an external file name (existing or to be created) in double quotes or a file from the resource cache in single quotes. Of course, a variable containing either of these types of values may also be used. If no name is specified, a temporary file will be created, which will be destroyed when the savefile is no longer in use. If a resource cache is specified, a temporary file will be created and the contents of the cached file will be copied into it. Changes will therefore only be temporary.