DB2: Is it good to create the LONG table space to use 32 KB data page
Check out the general answer I gave to you on your other question.

If you are storing your XML as a LOB, then I guess I'd see what is the common average size per table. If the average size is 4MB or less (which it sounds like), then you'd only need a 4K tablespace (see Space requirements for table, table 1).

If you are storing the XML as an XML data type in DB2, then you actually get some performance gains over LOB, especially if you inline the XML (and aren't doing updates to it all that often). This may be the best since you mention sizes less than 32K. You may wish to check out XML storage page for in-lining XML within the table vs outside for XML storage.