From:Steve Adams
Date:09-Dec-2000 06:39
Subject:   SCN

SCN means "System Change Number" not "System Commit Number". The V$ views consistently use columns named CHANGE# to report SCN values. Also, Rama Velpuri who is the authority on such matters defines SCN as "System Change Number" in his book Oracle8i Backup & Recovery.

However, because the SCN is always incremented at commits and seldom otherwise, it is OK to use the two terms interchangeably. This is at variance with what is taught by some Oracle instructors and reflected in the article The Dual Personalities of SCN on the OraGeeks web site. They use the term "System Change Number" for the block version number that is found in block headers and change vectors. The block version number is comprised of an SCN and a sequence number representing the number of changes that have been applied to the block at that SCN. Block version numbers are not unique (unless combined with a database block address) thus this incorrect use of the term "System Change Number" is potentially confusing and should be avoided.

Does the term SCN mean "System Commit Number" or "System Change Number"?