Rajeev,

If you DON'T specify DISABLE STORAGE IN ROW for your LOB
clause, Oracle will put lob contents in row itself. If
length of LOB column becomes more than 4000 bytes, Oracle
will move contents out of row.
If you DISABLE STORAGE IN ROW CACHE, only LOB locator is
stored in table, which takes less space.

Having first 4000 bytes in Row itself will make Full Table
Scan costly for that table.

FTS-->Full Table Scan

HTH

np70