DP4 helps you to maintain your database by reminding you to take backups at regular intervals. Back up the database in any of the following circumstances:
You make structural changes to a database.
DP4 warns you that the database is due to be backed up. (You should set a suitable maximum interval between backups using DFSETUP. See Setting up Transaction and Roll-back logging.
DP4 warns you that the transaction log file is approaching its maximum size. If a set limit has been reached, the database manager allows you to read records on the database, but not to update them.
You wish to copy or move the database to another system. In this case, back up the database to removable media, and use the database restore utility on the destination system. The procedure is the same if the destination system has a different operating system. (Of course if you have a direct network connection to the other machine it will be much easier to copy the database files directly.)