insert into tab1(val) values('...')

create table tab2(
id integer primary key generated always as identity,
val varchar( 50 ));
create table tab3(
id integer primary key generated always as identity,
val varchar( 50 ));

 public   static   void  restartGenerator(String tableName,  int  restartValue) {
	 try  {
		Connection conn = DriverManager
				.getConnection("jdbc:derby:c:/Derby/database/try");
		Statement stmt = conn.createStatement();
		StringBuilder query =  new  StringBuilder();
		query.append("alter table ");
		query.append(tableName);
		query.append(" alter column id restart with ");
		query.append(restartValue +  1 );
		System.out.println("query: " + query.toString());
		stmt.execute(query.toString());
		conn.close();
	}  catch  (SQLException e) {
		e.printStackTrace();
	}
}

create procedure restart_generator(
	in tablename varchar( 100 )
	, in restart_value integer
) parameter style java language java
external name 'org.degree.derby.DerbyProcedures.restartGenerator';

create trigger tab2_id_trigger after insert on tab2
referencing  new  as new_row
 for  each row mode db2sql
call restart_generator('tab3',new_row.id);

create trigger tab3_id_trigger after insert on tab3
referencing  new  as new_row
 for  each row mode db2sql
call restart_generator('tab2',new_row.id);