I am having some doubts regarding the System Change
1. What is the minumum and maximum value of SCN?.
2. What will happen if the SCN reaches the maximum value ?. If it gets resetted to 0(or minimum), then how the read-consistency is maintained ?. Oracle determines the read-consistency and take the data for SQL queries from rollback segments based on the SCN value and hence how that mechanism works in this situation.
I believe it starts with 0. About the maximum value - look at the next answer
2. What will happen if the SCN reaches the maximum value ?. If it gets resetted to 0(or minimum), ............
Quoting from the book "Oracle Backup and Recovery Handbook" by Rama Velpuri:
"SCN values never get reset to zero unless the database is re-created. You don't need to worry about running out of SCN's - even if you were to commit 16,000 transactions per second, it would take more than 500 years to run out of SCN numbers."