has anyone encounter this problem--update to be null value?(goldengate)

 recently I  open the supplemental log on database level, but not on table level.

I want to add supplemetal log on just one column of the table. This column can act as the virtual PK in the table, while this table has no PK and unique key. I configure in the extract and replicate ‘s parameter file: table table_name, keycols(column1); map table table_name,target table_name , keycols(column1);

  And in sql-plus , I execute the sql : alter table source_table_name add supplemental log group group_name (column1) always. Here just one column is added supplemental log.

When I do the update action on source table, the target table can be synchronized. But the trouble is :there is one column in target table, which is not virtual key and is not updated column , is updated to be null values. It means, there are 3 columns:A,B,C. A column acts virtual PK, I execute the sql: update source_table set B=values1 where A=value2;