Hi Deb,
The Snap Creator DB2 plugin does not backup an instance it backs up one or more databases. You must specifcy database. If you have multiple databases on the same host you can do this as well. Below is example:
DB2_CMD=C:\IBM\SQLLIB\BIN\db2cmd.exe -c -w -i Z:\IBM\SQLLIB\BIN\db2.exe
DB2_DATABASES=db1:user1;db2:user2;db3:user3
Regards,
Keith