3. The server records row lock information in the data block.
4. The server process writes the changes to the redo log buffer.
5. The server process copies the old image of the employee data about to be
changed to a rollback segment. Once the server process has completed this
work, the process modifies the employee data, which includes writing the SCN
to the ORA_ROWSCN pseudocolumn in Oracle Database 10g or newer database
releases.
6. Client B modifies the employee name on the screen and sends a SQL UPDATE
statement to the server.
7. The server process obtains an SCN and reads the data block containing the target
row.
8. The server process sees that there is a lock on the target row from the information
in the header of the data block, so it takes one of two actions. If the
isolation level on Client B??™s transaction is READ COMMITTED, the server
process waits for the blocking transaction to complete. If the isolation level for
Client B??™s transaction is SERIALIZABLE, an error is returned to the client.
9. Client A commits the transaction, the server process takes the appropriate
action, and the server sends a message to Client A confirming the commit.
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