SCN,Log sequence number

Hi
what is SCN(system change number),log sequence number.....
how it is useful.....
wt they do...
Thanks and Regards.

read more you must

Concern what about parv say.
Scn (system change number)—WHAN a transaction is committed a SCN number is generate.

Log sequence number –when a log switch occur than a log sequence number is generated.

Now u ask what the log switch??

So please read the chapter REDO LOG FILE from any oracle 8i,9i,10g database book.
Its easy for u:D .