How SCN sync after the tablespace is put back to END Backup mode

Question

When we put the tablespace in begin backup mode, the scn get forzen and it will not be further updated, until it is put back to end backup.
Question is : If at the time of being backup , say the snc forzed at 45. Before we put back the tablespace to end back up , we had genrerated 10 SCN. Then the current scn is 55. If we put the tablespace in end backup , does the datafile will start with scn 56 ( by maintaint it previous scn at 45)
Or after we put back the tsp in end back up , does the datafile will be updated from 46 to 55 , before it is updated with scn 56.
In the above example i am considering by db has one datafile only.
Thanks
Naveen

Answer 1

Are you implying that the "Checkpoint number" is a different series of numbers --
seperate from SCNs ?
Are you implying that when a checkpoint occurs it is this "Checkpoint number"
that is incremented and written to the datafile headers ?
There really is no such thing as a "Checkpoint number".
If you look at the definitions of V$DATABASE , V$DATAFILE and V$DATAFILE_HEADER, you would see that a Checkpoint increments the SCN.
A header can have multiple entries -- a Checkpoint SCN (called CHECKPOINT_CHANGE#) , ArchiveLog SCN (called ARCHIVELOG_CHANGE#),
the Current SCN (called CURRENT_SCN), SCN of last Unrecoverable (Nologging)
(called UNRECOVERABLE_CHANGE#) etc etc. They are all derived from SCNs
only.
The SCN is used as the single point of reference. Thus, we can compare
CHECKPOINT_CHANGE# with CURRENT_SCN with UNRECOVERABLE_CHANGE# etc.