Logging Primary Keys

Question

Hi
I´m looking for a way to log the primary keys from many tables in a unique table and column.
I thought to use xmltype column (like below) but I´m would like to hear another opinion about it.
Record 1:
'<TABLE>'
' <NAME>TB_ABC</NAME>'
' <PRIMARY_KEY>'
' <COLUMNX>XYZ</COLUMNX>'
' </PRIMARY_KEY>'
'</TABLE>'
Record 2:
'<TABLE>'
' <NAME>TB_DEF</NAME>'
' <PRIMARY_KEY>'
' <COLUMNA>123</COLUMNA>'
' <COLUMNB>456</COLUMNB>'
' </PRIMARY_KEY>'
'</TABLE>'
Record ...
Any problem to do that ? Performance risks ? Another better way ?
Thanks in advance.
Oracle 9iR2.

Answer 1

Well, the goal is to log the changes made in some tables.
Actually, in many tables there is a a trigger "Before update" to save the changes made (old/new values) and they are stored in a specific table that contains some columns as: Owner, Table_Name, Primary_Key ( columns separated by "+" delimiter in a varchar2 ), column_name, old_value, new_value, Date_Log ... ).
That is a control, but I would like to change the way that the primary keys are kept.
Based on that, I thought to replace the primary_key column to xmltype to facilitate the query and allow to use the xml functions.
In my test it worked fine, I got to find the records in a simple query and become more flexible, look:
Select Onwer, Table_Name, Column_Name, Old_Value, New_Value, Date_Log
From Table_Log a
Where a.Primary_Key.Extract('/TABLE/NAME/text()').getStringVal() = 'TB_ABC'
and a.Primary_Key.Extract('/TABLE/PRIMARY_KEY/COLUMX/text()').getStringVal() = 'XYZ'
Thanks in advance