User Preferences include the Operation > Compress File on Exit option.
We recommend that this option is left in its default Off state.
If selected it will only compact the file's structured storage removing elements marked for deletion.
It will not include any of the compress options found in the Compress Options dialog.
Search MicroStation help using "Compress Options Dialog" (include the quotation marks to search for the phrase) for details of the options available and related topics.
Please Note : If you access files over network and/or do not have a good file back-up system in place, then do not use this option.Better options would be to take a back-up of the file and then manually compress (File > Compress > Design) for individual files of use batch processing to compress groups of files.
Site Standards #3 - User Preference Seeds for a method of setting the initial state of the 'Compress File on Exit' preference.
Uncompressed files are not deleted
An earlier Ask Inga tip:
Configure your compress options