You can double-click on the files on the GUI and on version 2.3 of VMS and 2.x of IPS MC, and change the file size. The next time the pruning daemon runs, it ideally prunes these files, and the daemon runs automatically.
Stop the VMS services and run this command in order to truncate manually is the idsmdc.log file:
Run the net start crmdmgtd command in order to restart the service.
Note: If the DB file becomes too big, it can lead to database corruption. So it is recommended to regularly prune that file. Database pruning does not reduce the size of the database itself (the .db and .log files). The database deletes records, but it does not return the memory to the operating system. It marks it as free and keeps it internal to the database for re-use. When pruning runs, the .db file remains about the same size and the .log file actually grows.
In addition, you can move the files in this directory, \CSCOpx\MDC\Sybase\Db\IDS\AlertPruneData, to a backup or other file server, as these contain pruned events that you might want to restore. In this way, you can free up some space.