TSM Backup Methodology
From Backup Central
TSM can perform the following type of backups:
TSM performs a full backup upon the first time it backups a client. After that it performs incremental backups or selective backups depending upon how it's configured. A client's business requirements dictate how often and for what data upon initial client setup. If a client wants to be able to recover 7 versions of data then TSM would perform a full backup on the initial backup and then incrementals for the next 6 times the data changes or the next 6 days if you're doing selective backups. You'd define how long to keep those versions and the last version on the TSM server. Again, your business requirements dictating data retention.
TSM performs archives upon defining a schedule and associating clients to them. Your business requirements dictate what will be archived and for the retention period. By default, TSM does not delete the data from the client upon archiving it. Archiving is used to store specified data for longer periods of time such as 7 or 10 yrs., etc.
There is an option on the archive command line command to delete archived files (-DELETEFILES). This can be useful for periodic houskeeping jobs, but the default is to leave the source files as they are.