To create a baseline of performance of the system, one create a baseline and used for later comparisons. If a snapshot id passed in is invalid the procedure will return an error message indicating it is invalid. The snapshot baseline will be kept till it is dropped manually.

SQL> EXEC dbms_workload_repository.create_baseline(start_snap_id=>1, end_snap_id=>10, baseline_name=>'First baseline');

-- If cascade is TRUE, it will also drop the snapshot in the baseline.
-- If cascade is FALSE, it will only drop the baseline (not the snapshot)
SQL> EXEC dbms_workload_repository.drop_baseline(baseline_name=>'First baseline', cascade=>false);

-- view baseline name, start and end snap id
SQL> select BASELINE_NAME, START_SNAP_ID, END_SNAP_ID from dba_hist_baseline;