GRANT OPTION

if a user has the GRANT OPTION he can pass this privilege on to other users through a view, without granting the privilege on the original source view:
SQL> grant select on dba_users to dbatest with grant option;
SQL> conn dbatest
SQL> create view da_users as select * from sys.dba_users;
SQL> grant select on da_users to dbatest2;
SQL> conn dbatest2
SQL> select count(*) from dbatest.da_users;

COUNT(*)
----------
40

SQL> select count(*) from sys.dba_users;
select count(*) from sys.dba_users
*
ERROR at line 1:
ORA-00942: table or view does not exist


DG broker connections

setevent = '16634 trace name context forever, level 1'and restart the Data Guard Broker Process. This will record all Connectstrings used by the Data Guard Broker in the DRC.LOG-Files. So you can see which exact Connect is actually being used by the Data Guard Broker

metalink: [ID 745201.1]

to start and top dgbALTER SYSTEM SET DG_BROKER_START=[TRUE/FALSE];

SQL trace file interpretation

http://wiki.oracle.com/page/Structure+of+an+Extended+SQL+Trace+file


XCTEND rlbk=%d rd_only=%d
XCTEND A transaction end marker.
rlbk 1 if a rollback was performed, 0 if no rollback (commit).
rd_only 1 if transaction was read only, 0 if changes occurred.

prefetch

Execution plan looking like this:

---------------------------------------------------------------------------
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=322 Card=319 Bytes=11803)
1 0 TABLE ACCESS (BY INDEX ROWID) OF 'TARGET' (Cost=2 Card=1 Bytes=29)
2 1 NESTED LOOPS (Cost=322 Card=319 Bytes=11803)
3 2 TABLE ACCESS (FULL) OF 'DRIVER' (Cost=3 Card=319 Bytes=2552)
4 2 INDEX (RANGE SCAN) OF 'T_PK' (UNIQUE) (Cost=1 Card=1)


is using a feature called 'prefetch'.

More about it:
http://www.oracle.com/technology/products/oracle9i/daily/dec17.html
http://forums.oracle.com/forums/message.jspa?messageID=4236898