ora-01422: exact fetch returns more than requested number of rows

Oracle Documentation says:

“If possible, each table for which changes are applied by an apply process should have a primary key. When a primary key is not possible, Oracle recommends that each table have a set of columns that can be used as a unique identifier for each row of the table. If the tables that you plan to use in your Oracle Streams environment do not have a primary key or a set of unique columns, then consider altering these tables accordingly.”

And then it says:

“In the absence of substitute key columns, primary key constraints, and unique key constraints, an apply process uses all of the columns in the table as the key columns, excluding LOB, LONG, and LONG RAW columns. In this case, you must create an unconditional supplemental log group containing these columns at the source database. Using substitute key columns is preferable when there is no primary key constraint for a table because fewer columns are needed in the row LCR.”