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Current_SCN how it populates?

My friend has asked this question today as he got the same in one his interview...

The common answer we give is from any base table as v$database (current_scn) is populated by any base table.

However the base table is $KCCDI under column DICUR_SCN is current SCN. you can find this by querying the v$database view code in dba_views.

Lets look

	SQL> select current_scn from v$database;

	CURRENT_SCN
	-----------
	102707163


	SQL> select DICKP_SCN,DICUR_SCN from X$KCCDI;

	DICKP_SCN        DICUR_SCN
	---------------- ----------------

	102711050        102711285

	SQL> select current_scn from v$database;
	CURRENT_SCN
	-----------
	102711289
Note: DICKP_SCN is last checkpoint SCN, when the log switch happens then checkpoint will occur that SCN.

Further why this question has been asked I don't know, but this way we can find the interval of last checkpoint SCN as well. by DICKP_SCN - DICUR_SCN and then map to SCN_TO_TIMESTAMP.

-:)

February 13th, 2014 | Category: Administration

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