> Provide a sample.

Joe log in and insert "1" into TABLE_A.
Bill log in and insert "2" into TABLE_A.
Linda log in and after "select * from table_a" gets "1" only.
Why? Joe's TABLE_A isn't Bill's TABLE_A, but Linda is using synonym
to Joe's table.
Now, imagine that TABLE_B has FK to TABLE_A and Linda want to insert
reference to record "2" because Bill said that he put the record there.
I call this "a mess".

SY, SD.