OCA 04 - Managing the Oracle Instance

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04 - Managing the Oracle Instance

By Muhammad Asghar Khan

Reference: OCA Oracle Database 11g - Admin I Exam Guide by John Watson


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Agenda

http://asghars.blogspot.com

Components Required for Database Startup

Starting a Database Control Starting the Database Listener

Connecting to Database

Database Startup Database Shutdown

Setting Database Initialization Parameters

EXERCISE 4-1: Query and Set Initialization Parameters

Using the Alert Log and Trace Files EXERCISE 4-2: Use the Alert Log

Data Dictionary and Dynamic Performance Views

EXERCISE 4-3: Query Dynamic Performance Views

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The three components (database instance, databaselistener, and optionally Database Control) have theirown command-line utilities that can be used for startup

In single instance environment Oracle Corporations

recommended sequence for starting a database is tostart Database Control, then the database listener, andthen the database

Starting a Database Control

Database Control is a tool for managing only onedatabase

The configuration of Database Control will have beendone at database creation time

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To start Database Control, use the emctl utility. This willbe located in the ORACLE_HOME/bin directoryemctl start|status|stop dbconsole

For any of these commands to work, three environment

variables must be set: PATH, ORACLE_HOME, and

ORACLE_SID

Figure shows the startup of Database Control

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To connect to Database Control, use any reasonably up-to-date browser with URL https://hostname:port/em

The port number can be find by using the emctl status

dbconsole command or alternatively, you can look in the

file ORACLE_HOME/install/portlist.ini

To see the Database Control logon window the database

listener and instance must be running

Starting the Database Listener

The database listener is a process that monitors a port fordatabase connection requests

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There are three ways to start the database listener: With the lsnrctl utility

With Database Control

As a Windows service (Windows only)

The lsnrctl utility is in the ORACLE_HOME/bin directory.The key commands are:lsnrctl start|status [listener]

Where listener is the name of listener

Figure on next slide shows the startup of default listener

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An instance may be started and stopped

A database is mounted and opened, and thendismounted and closed

This can be done from either SQL*Plus or through

Database Control Ordinary users cannot start up or shut down a database

This is because ordinary users are authenticated againstdata dictionary which cannot be read until the database

is open

You must therefore connect with some form of externalauthentication: i.e by OS or external password file

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The syntax of the CONNECT command tells Oraclewhat type of authentication you wish to use: the

default of data dictionary authentication, password

file authentication, or operating system

authentication

These are the possibilities:connect user/pass[@connect_alias]

connect user/pass[@connect_alias] as sysdba

connect user/pass[@connect_alias] as sysoper

connect / as sysdba

connect / as sysoper

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In these examples;

The connect_alias will be resolved to a connect string, thisis necessary if the connection is to be made across anetwork

The first example is normal, data dictionary,

authentication The second two examples instruct Oracle to go to the

external password file to validate the username/passwordcombination

The last two examples use operating system

authentication; Oracle will go to the host operatingsystem and check whether the operating system userrunning SQL*Plus is a member of the operating systemgroup that owns the Oracle software

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Database Control will by default attempt to connectthrough a listener, but it can also use operating systemauthentication

SYSOPER and SYSDBA are special privileges with

special capabilities They can only be enabled when users are connecting

with an external authentication method: eitheroperating system or password file

You may be wondering what Oracle user you areactually logging on as when you use operating systemauthentication

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Issue the show user command The SYSDBA privilege logs you on to the instance as user

SYS

The SYSOPER privilege connects you as a user PUBLIC

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Database Startup


When you start up a database, you create an instanceof that database and you determine the state of the

database

When you issue a startup command, Oracle will

attempt to locate a parameter file

There are three default filenames. On Unix they are:

$ORACLE_HOME/dbs/spfileSID.ora

$ORACLE_HOME/dbs/spfile.ora

$ORACLE_HOME/dbs/initSID.ora

Oracle will work its way down the list, using the first file

it finds and ignoring the rest. If none of them exist, the

instance will not start

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Database Startup


The startup process is staged: whenever you issue astartup command, it will go through these stages:

SHUTDOWN

NOMOUNT

MOUNT

OPEN

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Database Startup


SHUTDOWN State When the database is SHUTDOWN, all files are closed

and the instance does not exist

NOMOUNT State

In NOMOUNT mode, the instance has been built in

memory (the SGA has been created and the

background processes started, according to the

parameter file), but no connection has been made toa database

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Database Startup


The startup process with NOMOUNT mode isdescribed graphically in the figure

Database is started in NOMOUNT

state during:

Database Creation

Re-creation of Control Files

Backup & Recovery Scenarios

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Database Startup


MOUNT State Mounting a database includes :

Associating database with instance

Instance locates and reads the control file using

control_files parameter Obtaining names & statuses of data and online redo log

fiels by reading the control file

Database is started in MOUNT state during:

Renaming data files

Enabling & disabling online redo log file archiving

Performing database recovery

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Database Startup


The startup process with MOUNT mode is describedgraphically in the figure

OPEN State

Opening database includes: Opening data files

Opening online redo log files

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Database Startup


In OPEN state all the data files and online redo logfiles are checked fro consistency, if required the

SMON perform the instance recovery

The overall startup process is described graphically

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Database Startup


Altering database states Mount the database

Open the database

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Database Shutdown


Shutdown require either a SYSDBA or a SYSOPERconnection

Following are the different shutdown modes:

NORMAL

TRANSACTIONAL IMMEDIATE

ABORT

NORMAL

In normal shutdown, no new connection is allowed andthe database will wait for all currently connected users todisconnect

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Database Shutdown


Typically, a normal shutdown is useless: there is always

someone logged on, even if it is only Database Control

itself

TRANSACTIONAL

In transactional shutdown mode no new connectionand transcation is allowed, wait for all the

transactions to complete

It prevents clients from losing work

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Database Shutdown


IMMEDIATE In immediate shutdown mode no new connection

and transaction is allowed, any uncommited

transactions are rolledback and disconnects all

connected users Next startup will not require instance recovery

ABORT In abort mode no new connection and transaction is

allowed, uncommited transactions are not rollback

and all connected users are implicitly disconnected

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Database Shutdown


Next startup will require instance recovery

A shutdown abort will not damage the database, butsome operations (such as backups) are not advisable afteran abort

The normal, immediate, and transactionalshutdown modes are usually referred to as clean,consistent, or orderly shutdowns

In clean shutdowns:

PMON will roll back any incomplete transactions

Then a checkpoint is issued, which forces the DBWn towrite all updated data from the database buffer cachedown to the datafiles

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Database Shutdown


LGWR also flushes any change vectors still in memory

to the log files

The abort mode, sometimes referred to as a

disorderly shutdown, leaves the database in an

inconsistent state

Which must be repaired by instance recovery

There is a startup command startup force that can

save time. It is two commands in one: a shutdownabort followed by a startup

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The parameters used to build the instance initially

come from either the parameter file (pfile or spfile) or

from defaults

Every parameter has a default, except for the DB_NAME

parameter; this must always be specified These parameters are divided into basic and

advanced

Most database instances will run well with defaultvalues for the advanced parameters

Only about thirty-three (the exact number may vary

between versions) are basic which may need to be set

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Parameters that can be changed while the instanceis running called dynamic parameters while static

parameters are fixed at instance startup time

To view the parameters and their current valuesselect name,value from v$parameter order by name;

select name,value from v$spparameter order by name;

V$PARAMETER shows the parameter values

currently in effect in the running instance while

V$SPPARAMETER shows the values in spfile on disk

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The views can also be seen through DatabaseControl. From the database home page, take the

Server tab and the Initialization Parameters link

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To change a parameters with SQL*Plus, use theALTER SYSTEM commandalter system set parameter_name=value scope=memory|spfile|both;

Note; If the instance is started with a pfile, then

SCOPE=SPFILE will fail To create spfile from pfile

create spfile='spfilename' from pfile='pfilename';

To create pfile from spfilecreate pfile [='pfilename'] from spfile [=' spfilename'] ;

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To view the basic parameters and their currentvalues

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EXERCISE 4-1: Query and Set Initialization

Parameters


1)

Run sqldeveloper

2) Connect as user SYS, with the SYSDBA privilege

3) Check whether basic parameters have all been setor are still on default

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EXERCISE 4-1: Query and Set Initialization

Parameters


4)

All the basic parameters should be considered,investigated to see if the default is appropriate

5) Change the PROCESSES parameter to 200. This is a

static parameter. The next illustration shows how

to do this by specifying a SCOPE and thenbouncing the database

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Using the Alert Log and Trace Files


The alert log (alert_ SID.log) is a continuous record of

critical operations applied to the instance and the

database

Alert log location is determined by the instance

parameter BACKGROUND_DUMP_DEST For many DBAs, the first thing they do when they are

asked to look at a database for the first time is locate

the alert log and scan through it, just to get an idea of

what has been going on

The trace files are generated by the various background

processes, usually when they hit an error

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Using the Alert Log and Trace Files


These files will also be located in theBACKGROUND_DUMP_DEST directory

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EXERCISE 4-2: Use the Alert Log


1.

Find the value of the BACKGROUND_DUMP_DESTparameter

2. Navigate and open the alert log

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The data dictionary is metadata: data about data User definitions, security information, integrity

constraints, and (from release 10 g onward)

performance monitoring information are all part of

the data dictionary

It is stored in the SYSTEM and SYSAUX tablespaces

To query the dictionary, Oracle provides a set of

views. The views come in three forms, prefixedDBA_, ALL_, or USER_

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Any view prefixed USER_ will be populated with

rows describing objects owned by the user querying

the view

Any view prefixed ALL_ will be populated with rows

describing objects to which you have access (givenpermission)

Any view prefixed DBA_ will have rows for every

object in the database Some of those commonly used by DBAs are:

DBA_OBJECTS

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DBA_DATA_FILES

DBA_USERS

DBA_TABLES

DBA_ALERT_HISTORY

The dynamic performance views give access to aphenomenal amount of information about theinstance, and (to a certain extent) about thedatabase

The dynamic performance views are created atstartup, updated during the lifetime of the instance,and dropped at shutdown

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Dynamic performance views are populated from

the instance or the controlfile

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EXERCISE 4-3: Query Dynamic Performance Views

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1. Determine what datafile and tablespaces make up

the database

2. Determine the location of all the controlfile copies

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OCA 04 - Managing the Oracle Instance

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