You can check the status of the last backup in 4D 2004 by using the GET BACKUP INFORMATION command or by checking the Last Backup Information under the Backup->Configuration setting of the database preferences.

The GET BACKUP INFORMATION command allows you to get related information on the last backup performed. To get the status of the last backup, you simply pass selector type 2 as the first parameter e.g. GET BACKUP INFORMATION(2;info1;info2). When this command is executed, the second and third parameters of the command will contain the error number and the status information (in text) respectively.
Another way to check the backup status is to simply access the database preferences and check the Last Backup Information in the backup configuration setting.