This is probably the oldest type of backup. The process is simple, backup software starts at the beginning of a file structure and copies all of the data until it reaches the end, resulting in a backup. What can make this backup inconsistent is that if any user added/modified after a backup but before it completed that would result in an inconsistent backup; the files in the backup are not consistent. For databases these types of backups do not provide adequate protection because they only capture what is on disk. Example, with SQL Server there are a several different files, primary (MDF), log (LDF) and secondary (NDF) files and there could be I/O (transactions) that are still in memory. The inconsistent backup method only captures what is on disk and in the case of a database there may be transactions still in memory.