There are lots of restrictions in a READ ONLY transaction:

* You can not switch to READ WRITE mode.

* You can not run any INSERT, UPDATE, DELETE statements.

* You can run SELECT query statements.

The tutorial exercise below shows you some of the restrictions:

SQL> connect HR/globalguideline

SQL> SET TRANSACTION READ ONLY;

Transaction set.

SQL> SET TRANSACTION READ WRITE;

ORA-01453: SET TRANSACTION must be first statement of

transaction

SQL> INSERT INTO ggl_links (url, id)

2 VALUES ('sql.com', 113);

ORA-01456: may not perform insert/delete/update operation

inside a READ ONLY transaction

SQL> DELETE FROM ggl_links where id = 110;

ORA-01456: may not perform insert/delete/update operation

inside a READ ONLY transaction

SQL> SELECT * FROM ggl_links;

  ID URL   NOTES  COUNTS CREATED

------- ---------------- ---------- ---------- ---------

 101 globalguideline.COM     07-MAY-06

 110 globalguideline.COM     07-MAY-06