If it finds one, it reuses it. Otherwise, it checks the statement for
syntax and evaluates it to determine the best way to execute it. This processing
of the SQL statement is called parsing and optimizing. (The optimizer is
described in more detail in Chapter 4.) Once the processing is done, the statement
is cached in the shared SQL area.
3. The server process copies the old image of the employee data about to be changed
to a rollback segment and to a redo seqment. The rollback segment changes are
part of the redo. This may seem a bit odd, but remember that redo is generated
for all changes resulting from the transaction. The contents of the rollback segment
have changed because the old employee data was written to the rollback
segment for undo purposes. This change to the contents of the rollback segment is
part of the transaction and therefore part of the redo for that transaction.
4. Once the server process has completed this work, the process modifies the database
block to change the employee name. The database block is stored in the
database cache at this time.
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