Lesson 3	Initialization file
Objective	Identify the types of information contained in the initialization file.

Oracle Initialization File and Parameters

The database initialization file is a text file containing a number of parameters that control how the Oracle database works. At a very high-level, you could categorize those parameters as:

A pointer to the database control files
Information about the database itself, such as the physical block size used when reading and writing datafiles
Parameters that control the Oracle background processes
Parameters that control how Oracle allocates memory
Pointers to the directories containing the alert log and trace files for the instance

Here are some lines from a typical initialization file:

db_name = devl
db_files = 1024
control_files = 
 (/m01oracle/oradata/SCTPROD/control01.ctl,
  /m21/oradata/SCTPROD/control02.ctl,
  /m57/oradata/SCTPROD/control03.ctl)
db_block_size = 8192

Parameter Details

There are many parameters that you can set in the initialization file. Oracle documents all of them in the Oracle Server Reference Manual. Look through the following SlideShow to learn about the most important parameters in a bit more detail:

Important Oracle Initialization Parameters

1) The db_name parameter names the database. In this case, the name is dev1. When you SELECT name FROM v$database, this is the name that you see.

2) The db_files parameter controls the total number of database files that may be open at any one time. This includes control files, redo log files, and datafiles. You should set this value a bit higher than the total number of files in your database. That allows you to add new datafiles without stopping and restarting the instance.

3) The control_files parameter points to the database control files.

4) The db_block_size parameter controls the physical size of a database block.

5) Oracle buffers data in memory in order to reduce disk I/O.

6) The shared pool is an area that Oracle uses to store and parse SQL statements and PL/SQL code.

7) The log_buffer parameter controls the amount of memory Oracle uses to buffer data that needs to be written to the redo log files.

8) This value controls the maximum amount of memory that Oracle will use to sort data when executing a query.

9) After a large sort, Oracle will attempt to release some of the memory used by that sort.

How the Initialization File works

Oracle reads the initialization file whenever you start an instance.
Any changes that you make to the initialization file afterwards will not take effect until you shut down and restart your system.
Strictly speaking, Oracle does not consider the initialization file to be part of a database.
here is why.
It is an important file though, and you want to preserve it with the same care that you do all the other files that are database files.

Initialization File - Exercise

First, click the Exercise link below to find and look at your database's initialization file.
Initialization File - Exercise