For each BLOB, CLOB, or XML column created for a table, the database automatically stores a 40-byte or 45-byte multiple field pointer in the row to the subtable that stores the actual BLOB, CLOB, or XML data for that column (see Sizing a LOB or XML Subtable). This value, called an OID, is stored in VARBYTE format.
If a BLOB, CLOB, or XML column is null, then so is its OID.
The column sizes reported here are for OIDs stored on disk in rows. The sizes do not include, and are not the same as, the sizes of OIDs passed as inline or deferred host parameters as part of a USING request modifier row.