IBM Tivoli Storage Manager is a backup & archive solution, so if you are familiar with backup solutions you will discover that TSM will have to be capable of performing four main functions: backup, restore, archive, and retrive. Although these concepts seem easy to most, many new admins have a hard time distinguishing between backup & archive. As I am trying to cover every one, below you will find a brief of each as being defined by IBM Tivoli Team.

Backup: Creates a copy of a file to protect against the operational loss of destruction of that file. Customers control backups by defining the backup frequency and number of versions.

Restore: Placesbackup copies of files into a customer-designed system or workstation after the loss of a file. by default, the most recent version of each active file requested is replaced.

Archive: Create a copy of a file or set of files for vital record retention of data, such as patent information, financial information, or customer records. Customers control archive by defining the retention period. This feature enables customers to keep unlimited archive copies of a file.

Retrieve: Allows users to copy an archive file from the storage pool to the workstation. The Archive copy in the storage pool is not affected.

Basically the main difference between archive and backup, is backup meant for the situation where you loose the data and you need to recover. In the other hand, you require the archive to meet certain auditing requirement of keeping certain data for a certain period of time.

I hope that clear up the differences between backup & archive for all.