We had an interesting question on AskTOM the other day about LOB compression. Someone was very concerned that after applying compression to the LOBS in the column of their table, the table actually got larger! Cue much confusion and panic, but after a little exploration, the explanation was pretty simple.
By default, when you create a LOB column in a table, the default storage definition is ENABLE STORAGE IN ROW. As per the documentation:
If you enable storage in row, then the LOB value is stored in the row (inline) if its length is less than approximately 4000 bytes minus system control information
