This chapter introduces major components of Oracle9i. The objectives important to this chapter are:
The text lists eighteen DBA management tools included in Oracle9i.
Ten tools are available only in Enterprise Manager:
Six tools are available only from a command line:
Only two are available from both Enterprise Manager and from a command line:
The text suggests that some tasks are more easily done with a command line utility, such as changing a password. The command line syntax in SQL*Plus is given:
ALTER USER user_ID IDENTIFIED BY new_password;
This method avoids the usual double entry of a password, which is slower. If you were going to reset several passwords, the command line method might be easier as well as faster.
The text goes on to discuss configuring Oracle Net for your installation. An Oracle Net component will reside on the server, and another component of it will reside on the workstation of any user of the system. Both must be configured to point to the same database, and both must be configured to use the correct protocols for your network. These settings are stored in a file that is stored on the client workstation and on the server: tnsnames.ora. This file stores the setting listed above, as well as pointers to databases on other servers.
On the server side, Oracle Net runs a service called the Listener. This service receives requests from the client, translates them from network protocol to Oracle protocol, and sends the request to the database. The port that the Listener uses, the names of the databases, and the names of the servers holding the databases are saved in the service name of the Listener. When logging on to the database, you will generally be prompted to provide your user ID, your password, and the service name of the Listener for your database. The service name goes in a field labeled Host String. (Just to be inconsistent?) You can get away with not entering the service name, if you are logging on the the server that holds the database. In this case, you leave the Host String field blank, and you will use the Oracle protocol called Bequeath, instead of Oracle Net to make the database connection.
The text reminds us that if we are connecting to a database on our network, we will use Oracle Net, if we are connecting across the Internet, we will use a Java tool such as JDBC, and if we are connecting by logging in on the server itself, we can use Bequeath.
Pages 34 through 40 walk you through creating a service on your database. Be aware of some key points:
These changes are saved in tnsnames.ora, which is saved in ORACLE_HOME\network\admin. The text cautions us to use only a plain text editor when making manual changes to this file. It will not work if you change it with Wordpad or Word, which will save control characters in it.
The text describes several processes that run in the background when you use Oracle. The application that the user runs to access the database is a foreground process. The first background process is the user process, which received requests from the user application. If you are using a dedicated server, your user process will have a dedicated server process. If you have a shared server, you may have several user processes sharing each server process, and connecting with them through a dispatcher. In either case, you use a connection that runs from the user process through the server process to the database.
The two main memory sections of an Oracle instance are the System Global Area and the Program Global Area. Each server process has its own PGA. Several background processes interact with the two sections of memory.
Five components of the SGA are listed:
Several background processes are described:
Oracle Enterprise Manager is discussed next. It is referred to as just Enterprise Manager. It can run as the OEM Console, or as the Enterprise Management Server.
Four main features are discussed in detail: