There is no equivalent to an Oracle ROWID in db2. You might want to use db2 IDENTITY property to get row number.
Alternate approach would be to use GENERATE_UNIQUE built-in function and store the unique data in a new column in the table. It would generate 13 bytes bit data (CHAR(13) FOR BIT DATA) that are unique across the system. The GENERATE_UNIQUE function is persistent across database reorganization and migrations. Below is an example of how it can be used in a insert statement. When it is used as the primary key.
INSERT INTO <tab_name> VALUES (GENERATE_UNIQUE(), ?, ?, ?)
Hope this helps.