Oracle SCN : System Change Number

System Change Number

SCN is a number generated in the database on the occurrence of an event in the database, the event could be

• DML statement execution
• SELECT statement execution
• DDL statement
• Commit statement

Whenever this type of transaction happens, the current timestamp converted into the system change number (SCN)

SCN is useful in MANY DATABASE SCENARIOS SUCH AS

• Instance Recovery
• Roll forward
• Rollback
• Backup and recovery 
• Read consistency

SCN is always incrementing because timestamps always increase.