Compressing a DGN file reduces its size and clears the undo buffer.
The COMPRESS DESIGN key-in is used to compress files. This key-in automatically minimizes the number of levels that are in the level name dictionary (a list of all levels used in references, including nested references, in the master file). It also trims down the size of the reference attachment, view group, and saved view elements.
The COMPRESS OPTIONS <ON, OFF, RUN, TOGGLE> key-in is used to open the Compress Options dialog.
A level name dictionary stores the name of every level in the master file and the name of every level in each reference file that has ever been attached to any model within the file. A level name dictionary is an internal implementation and users cannot access it.
Unless you are recording the open DGN file's design history
, compressing the file prevents previous changes from being undone.
To compress the open DGN file automatically when closing it, turn on Compress File on Exit in the Preferences dialog, Operation section(
Compression does not purge unused data resources from DGNLib files. Use the DELETE UNUSED key-ins