Managing an Oracle instance includes configuring parameters that affect the basic operation of the Oracle instance. These parameters are called initialization parameters. The Oracle instance reads initialization parameters from a file at startup.
During installation, when you select a preconfigured database workload available in Database Configuration Assistant (DBCA), the initialization parameters are optimized for typical use in the environment that you specified. As the number of database users increases and the workload increases, you might have to alter some initialization parameters. You can make these changes using the Initialization Parameter page in Oracle Enterprise Manager Database Express (EM Express), or by using an advisor provided by Oracle Database, such as the Memory Advisor. See "Optimizing Memory Usage with the Memory Advisors" for more information.
After being read from a file, initialization parameters are retained in memory, where the values for many of them can be changed dynamically. There are two types of parameter files. The type of file used to start the instance determines if dynamic initialization parameter changes persist across database shutdown and startup. The parameter file types are:
Server parameter file
The server parameter file, commonly known as the SPFILE, is the preferred form of initialization parameter file, and is a binary file that can be written to and read by the database. It must not be edited manually. It is stored on the host computer on which Oracle Database is running. Changes are made when you use EM Express or SQL*Plus to modify one or more initialization parameters, or when Oracle Database itself makes changes for self-tuning purposes. Any changes to it persist across database shutdown and startup operations.
When changing an initialization parameter in the server parameter file, you can also specify that the in-memory value be changed, so that your change is reflected immediately in the current instance. If you do not change the in-memory value, then the change does not take effect until you shut down and restart the database.
Text initialization parameter file
A text initialization parameter file is a text file that can be read by the Oracle instance, but it is not written to by the instance. You can change a text initialization parameter file with a text editor, but changes do not take effect until you restart the Oracle instance. When you start the instance with this type of file, you can still change many initialization parameters dynamically with EM Express, but only for the current instance. Unless you also edit the text initialization parameter file and make the same change, the change is lost when you restart the database instance.
You can use SQL statements to create the following:
A server parameter file from a text initialization file
A server parameter file from the current (in-memory) values of all initialization parameters
A text initialization parameter file from a server parameter file
When you create the database with DBCA, a server parameter file is created. This file is then used each time the database is started.
Oracle Database Administrator's Guide for information about the default name and location of the server parameter file, and for commands to create a server parameter file or text initialization parameter file
Oracle Database Concepts for an overview of parameter files