You backup DB2 data (I assume OS/390) with the COPY command.
The basic format is ==>
COPY TABLESPACE DBNAME.TSNAME
You can also add FULL YES/NO for full and incremential Image copies
and SHRLEVEL CHANGE/REFERENCE for the type of locking SHRLEVEL REFERENCE will allows users to only READ object you are backing up and SHRLEVEL CHANGE will allows users to chage data while backing up, please remember to do a QUIESCE ofter this type of backup to create a point of consistency.
There are other option to create onsite (COPYDDN) and offsite image copy (RECCOVERYDDN), you can use both.
DB2 also allows concurrent image copies but I would stear away from them as it really complicates recover, especially when recovering dropped objects and usingf DSN1COPY.
By the way you can also use the DSN1COPY utility for backing up your data.