DB2 9 for z/OS offers a new DDL parameter for your tables: APPEND. If you specify APPEND NO, which is the default, DB2 will operate as you are accustomed to it operating. That is, when rows are inserted or loaded DB2 will attempt to sequence them based on the clustering index key.
If you specify APPEND YES though, DB2 will ignore clustering during inserts and online LOAD processing. Instead of attempting to maintain clustering, DB2 will just append the rows at the end of the table or partition. If the table space is partition-by-growth (new DB2 9 feature) then DB2 can use any partition with space available at the end; for range-partitioned table spaces, obviously DB2 will append the data to the end of the partition corresponding to the range for the value(s) being inserted.
You might want to choose this option to speed up the addition of new data. Appending data is faster because DB2 does not have to search for the proper place to maintain clustering. And you can always re-cluster the table by running a REORG.
The APPEND option cannot be specified on LOB tables, XML tables, or tables in work files.
To track the state of the APPEND option there is a new column, APPEND, in the DB2 Catalog in SYSTABLES. Its value will be either ‘Y’ or ‘N’.