How To Experiment a Data Lock?

If you want to have some experience with data locks, you can create two windows runing two
SQL*Plus sessions. In session 1, you can run a UPDATE statements to create a data lock.
Before committing session 2, switch to session 2, and run a UPDATE statements on the same
row as session 1. The UPDATE statement will be put into wait status because of the data lock.
Follow the tutorial exercise below to experience yourself:
(session 1)
SQL> connect HR/fyicenter
SQL> SET TRANSACTION
ISOLATION LEVEL
READ COMMITTED;
Transaction set.
SQL> SELECT * FROM fyi_links;
ID URL NOTES
--- ---------------- --------
101 FYICENTER.COM
110 CENTERFYI.COM
SQL> UPDATE fyi_links
SET url='fyicenter.com'
WHERE id=101;
1 row updated.
(lock created on row id=101)
(session 2)
SQL> connect HR/fyicenter
SQL> SET TRANSACTION
ISOLATION LEVEL
READ COMMITTED;
Transaction set.
SQL> UPDATE fyi_links
SET notes='FAQ Resource'
WHERE id=101;
(wait for lock on row id=101)
SQL> COMMIT;
(lock on row id=101 released)
(ready to run UPDATE)
1 row updated.
SQL> SELECT * FROM fyi_links;
ID URL NOTES
--- ---------------- --------
101 fyicenter.com
110 CENTERFYI.COM
SQL> COMMIT;
SQL> SELECT * FROM fyi_links;
ID URL NOTES
--- ---------------- ------------
101 fyicenter.com FAQ Resource
110 CENTERFYI.COM