DATABASE backup question FULL or INCREMENTAL?

[David Browne.]

I am doing a nightly database full backup with ADSM/TSM.  (TSM 3.7.4 on
OS390/2.10)
What is most commonly done a Full or Incremental?
What are the advantages/disadvantages of a full over an incremental backup
of the servers database?
The command we enter is as follows:
                      backup db type=full devclass=dboffsite
 Where dboffsite is the a tape device class.