Lesson 11	State and structure of a database
Objective	Determine the state of your database system.

State Structure of Database

This lesson reviews the information presented in our project database. We will use the initialization files and V$ views to collect information about our database ORC1. Our ORACLE_HOME is c:\oracle8.

initorc1.ora

The initorc1.ora file is read by the instance during startup to determine where to find files and to set some parameters. This file should be backed up regularly and is usually located in ORACLE_HOME\DATABASE. This file points to where the control file(s) are located.

Control file

This file is read by the instance at startup and contains information to identify instance parameters and file placement. This file should be duplexed and must be backed up regularly. One copy of this file is usually found in ORACLE_HOME\database directory.

Redo log files

These files should be multiplexed and spread over multiple disk drives. The default location for these files is ORACLE_HOME\database. You need at least two redo logs for Oracle to work.

Archive log files

These files should be duplexed and contain information from the redo logs. They must not reside on the same disk as the redo logs. The default location for the archive logs is ORACLE_HOME\database/archive.

V$ views

Here is a list of all the V$ views:

V$SGA
V$INSTANCE
V$PROCESS
V$DATABASE
V$DATAFILE

V$LOG
V$LOGFILE
V$LOG_HISTORY
V$CONTROLFILE

What is the purpose of the V$INSTANCE file in Oracle?

In Oracle, the V$INSTANCE file is a dynamic performance view that provides information about the current instance of an Oracle database. An Oracle database can consist of one or more instances, each of which runs on a separate server or node and accesses a shared database. The purpose of the V$INSTANCE file is to provide real-time information about the current instance, including its status, configuration, and performance.
The V$INSTANCE file contains a number of different columns that provide information about the current instance, including:

INSTANCE_NAME: The name of the current instance.
INSTANCE_NUMBER: The number assigned to the current instance.
THREAD#: The thread number assigned to the current instance.
STATUS: The current status of the instance, such as ACTIVE, MOUNTED, or OPEN.
STARTUP_TIME: The time that the current instance was started.

The V$INSTANCE file is particularly useful for database administrators who need to monitor the status and performance of their Oracle database instances. By using the V$INSTANCE file, administrators can quickly identify instances that are experiencing problems, such as high CPU usage, slow queries, or database corruption, and take corrective action to resolve the issues.
Overall, the V$INSTANCE file is an important tool for managing and monitoring Oracle database instances, and is used extensively by database administrators and performance analysts to optimize the performance and reliability of their Oracle databases.

The next lesson wraps up the module.