Hi all,

I'm currently studying LUW's DB2 v8 at a Linux Redhat 4 Enterprise Edition in the "compression" section

I notice that there is value compression which would change row format so the new row format would :
- Make NULL stored with 3 bytes only
- Make VARCHAR, Long VARCHAR, and other variable-length data types consume 2 bytes less than usual
- Make INTEGER, CHAR, DECIMAL consume 2 bytes more than usual

Now, the question is, how does the old row format look like ??
At the old row format (before decompression), how would the data types stored ?
Isn't NULL always stored 3 bytes ? And when talking about 2 bytes less consuming variable-length data type, what does it actually mean ?

Variable length data types has 2 bytes of length part and 1 byte for the NULL indicator, right ? Will these part be "compressed" ???

NULL: the datatype length + 1 byte for null indicator
A null timestamp is 11 bytes, not null is 10
Variable Length: 2 bytes for max length value + actual data length
Varchar(30) = "foo" is 5 bytes (if nullable, then 6 bytes)

Actually, a nullable (but not null) timestamp takes 11 bytes; a not-nullable timestamp takes 10 bytes.

Question: does a nullable varchar field, when effectively NULL, always take exactly 3 bytes?