Installing and Running Oracle - Oracle Essentials - page 87

One of the great attractions of using the Oracle Database Cloud, described in detail in
Chapter 15 , is the ease of getting started. There is no setup or installation of an Oracle
Database. You simply request a Database Cloud Service from your browser and, within
minutes, you have a working environment available to you with the full power of the
Oracle Database.
But just because you don't have to install or configure an Oracle Database Cloud Service
does not mean that these tasks were not done. In fact, each Database Cloud Service is
implemented with a specific configuration that you cannot change, such as the amount
of storage you have selected as well as a variety of configuration options designed to
give you adequate computing and I/O without imposing on other users of the Database
Cloud.
When you access your Oracle Database Cloud Service, you do not use SQL*Net. You
communicate from a browser (or application via RESTful Web Services, described in
Chapter 15 ) with HTTP. The use of this common Internet protocol has two profound
implications. First of all, you cannot use SQL*Net over HTTP. This limitation means
you cannot simply move data from an on-premise Oracle Database to a Database Cloud
Service, modify your TNSNAMES.ORA file, and use the same application, as you would
if you moved your Oracle Database from one server to another.
Secondly, HTTP is a stateless protocol. This means that you cannot have a transaction
span multiple interactions with an Oracle Database Cloud Service. In many cases, this
limitation may not make any difference at all, but in some, it may cause you to modify
the way you implement your applications.
The Oracle Database Cloud, as well as other ways to use an Oracle Database in the cloud,
is the focus of Chapter 15 , but for now, understand that although the Oracle Database
is certainly well suited to deliver its functionality in a cloud computing environment,
the surrounding infrastructure used in the cloud is quite different from a traditional
deployment architecture, which means that the great benefits of the cloud will come
with some necessary accommodations.
Oracle at Work
To help you truly understand how all the disparate pieces of the Oracle Database work
together, this section walks through an example of the steps taken by the Oracle Database
to respond to a user request. This example examines the work of a user who is adding
new information to the database—in other words, executing a transaction.
Oracle and Transactions
A transaction is a work request from a client to retrieve, insert, update, or delete data.
(The remainder of this section will focus on transactions that modify data, as opposed
to retrieving data.) The statements that change data are a subset of the SQL language