I observed baan still uses char for string fileds if the back end is oracle.why it doesnt use varchar2?

regads
juvenile

Because varchar2 is not ANSI standard.

Refer to the link - Programmer's Guide to the Oracle Pro*C/C++ Precompiler (http://www-rohan.sdsu.edu/doc/oracle/server803/A54661_01/intro.htm)
VARCHAR2

A kind of column in the database that contains variable-length character data, up to 2000 bytes. This is what Oracle calls an "internal datatype", because it's a possible column type. See page 3-20.

[InstallableUnit]
Key = ERP_RuntimeTools_x86_SUSE
Name = Infor ES Porting Set Linux x86 SUSE and Red Hat {0}
Version = 8.6a
Build = PA.3918.32-bit
Type = portingset
SetupType = 0
BuildDate = 2009-10-30[10:23:07]

The Oracle database still uses the CHAR or NCHAR datatype for string columns and
does not support the VARCHAR2 or NVARCHAR2 datatype. This means that the
database consumes much more space than needed. Also the growth rate of the
database is higher than needed.

When the VARCHAR datatype is used a reduction of about 40% in database space is
expected.

I've test will reduce storage for 50%