RE: Porting Guide and Statement made about Char Vs VarChar

The Oracle porting guide has a similar statement:

"Many Oracle applications use the VARCHAR2 data type for very small character strings. In these
circumstances, it is better to port it to the fixed-length DB2 UDB data type CHAR(n), as it is more
efficient and takes less storage than the VARCHAR data type. The CHAR data type should always be used
for columns of 40 bytes or fewer."


Charles

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Scott Johnson
Sent: Tuesday, November 27, 2007 2:51 PM
To: MIDRANGE-L@xxxxxxxxxxxx
Subject: Porting Guide and Statement made about Char Vs VarChar

http://www-03.ibm.com/servers/enable/site/db2/porting.html

I have had a read thru the "DB2 for i5/OS porting guide:
MySQL to System i
platform" and found a very interesting statement made about
when to use
Char versus VarChar. Page 11 has this tidbit:
"The CHAR data type must always be used for columns of 40
bytes or fewer."

Why would IBM make such a strong statement that we use a Char
when the
field is less than 40 bytes in length? Would it still be the
case when I
have a 35 character field that over 75% of the time only contains 15
characters? What about a 10 character field that is mostly
only has data
that is 4 characters in length? I realize that with a
VarChar there are
the bytes tacked on to contain the length, but I must be
missing something
someplace.

Can someone with some deep dark knowledge of the internal
workings of DB2
for i5/OS give me some info on why IBM would say this.

Thanks,
Scott


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