Creating the Database Links
CREATE DATABASE LINK DNYTST10.world CONNECT
TO strmadm IDENTIFIED BY strmadm USING 'DNYTST10.world'
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Understanding the SCN values
The System Change Number (SCN) is the main
controlling function that is used to keep track of database
transactional activity. SCN is a stamp that defines a committed
version of a database at a particular point in time. Oracle
assigns every committed transaction a unique SCN. To support the
multi-version read-consistency capabilities, Oracle keeps
records of all database changes with the help of SCN numbers.
SCN is a running number for the database changes.
SCN is a vital tool utilized by the Streams
Methodology. The processes of reading, propagating and applying
database changes make use of the SCN numbers. SCN values provide
a time-based tracking number that can be used to coordinate the
various Streams processes. Based on SCN numbers, various Streams
processes are able to restart from where they left off when a
particular process is interrupted and has to be restarted.
Oracle provides a DBMS procedure that is
used to query the SCN that was in effect at any point. As shown
in the following SQL statement, the get_system_change_number
procedure shows the current SCN value of the database.
Select
DBMS_FLASHBACK.GET_SYSTEM_CHANGE_NUMBER() from dual
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During the database checkpoint, Oracle
records the SCN number into the control files and also all data
files. The same SCN number is recorded in all the files.
