A Transaction, Step by Step
This simple example illustrates the complete process of a transaction. The example
uses the EMP table of employee data, which is part of the traditional test schema
shipped with Oracle databases. In this example, an HR clerk wants to update the
name of an employee. The clerk retrieves the employee??™s data from the database,
updates the name, and commits the transaction.
The example assumes that only one user is trying to update the information for a row
in the database. Because of this assumption, it won??™t include the steps normally
taken by Oracle to protect the transaction from changes by other users, which are
detailed in Chapter 8.
The HR clerk already has the employee record on-screen and so the database block
containing the row for that employee is already in the database buffer cache. The
steps from this point would be:
1. The user modifies the employee name on-screen and the client application sends
a SQL UPDATE statement over the network to the server process.
2. The server process looks for an identical statement in the shared SQL area of the
shared pool.
Pages:
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194