Installing and Running Oracle - Oracle Essentials - page 77

SQLNET.ORA
Provides important defaults and miscellaneous configuration details. For example,
SQLNET.ORA contains the default domain name for your network.
For directory naming, you can either use an LDAP.ORA configuration file, described
below, or use a standard DNS server to locate the LDAP server:
LDAP.ORA
For Oracle8 i and later releases, the LDAP.ORA file contains the configuration in‐
formation needed to use an LDAP directory, such as the Oracle Internet Directory.
This information includes the location of the LDAP directory server and the default
administrative context for the server. This is no longer required for an LDAP server
that is registered with the Domain Name Server (DNS) since Oracle Database 10 g .
As mentioned in Chapter 2 , Oracle9 i added a server parameter file, named SPFILE ,
which provides storage for system parameters you have changed while your Oracle9 i
instance is running, using the ALTER SYSTEM command. With the SPFILE , these new
parameter values are preserved and used the next time you restart your Oracle instance.
You can indicate whether a particular change to a system parameter is intended to be
persistent (in which case it will be stored in the SPFILE ) or temporary.
The SPFILE is a binary file that is kept on the server machine. By default, an Oracle9 i
or later instance will look for the SPFILE at startup and then for an instance of the
INIT.ORA file.
The SPFILE can also be kept on a shared disk, so that it can be used to initialize multiple
instances in an Oracle Real Application Clusters configuration.
Starting Up the Database
Starting a database is quite simple—on Windows you simply start the Oracle services
(or specify that the services are started when the machine boots), and on Unix and Linux
you issue the STARTUP command from SQL*Plus, or through Enterprise Manager. While
starting a database appears to be a single action, it involves an instance and a database
and occurs in several distinct phases. When you start a database, the following actions
are automatically executed:
1. Starting the instance . Oracle reads the instance initialization parameters from the
SPFILE or INIT.ORA file on the server. Oracle then allocates memory for the System
Global Area and starts the background processes of the instance. At this point, none
of the physical files in the database have been opened, and the instance is in the
NOMOUNT state. (Note that the number of parameters that must be defined in
the SPFILE in Oracle Database 10 g and Oracle Database 11 g as part of the initial
installation setup have been greatly reduced. We described the initialization pa‐
rameters required in Oracle Database 12 c in Chapter 2 .)