OCA 04 - Managing the Oracle Instance
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Transcript of 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
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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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Components Required for Database Startup
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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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Components Required for Database Startup
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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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Components Required for Database Startup
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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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Components Required for Database Startup
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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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Components Required for Database Startup
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Connecting to Database
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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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Connecting to Database
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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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Connecting to Database
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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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Connecting to Database
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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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Connecting to Database
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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
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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
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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
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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
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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
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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
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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
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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
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Altering database states Mount the database
Open the database
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Database Shutdown
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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
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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
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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
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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
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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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Setting Database Initialization Parameters
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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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Setting Database Initialization Parameters
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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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Setting Database Initialization Parameters
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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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Setting Database Initialization Parameters
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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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Setting Database Initialization Parameters
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To view the basic parameters and their currentvalues
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EXERCISE 4-1: Query and Set Initialization
Parameters
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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
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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
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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
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These files will also be located in theBACKGROUND_DUMP_DEST directory
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EXERCISE 4-2: Use the Alert Log
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1.
Find the value of the BACKGROUND_DUMP_DESTparameter
2. Navigate and open the alert log
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Data Dictionary and Dynamic Performance Views
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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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Data Dictionary and Dynamic Performance Views
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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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Data Dictionary and Dynamic Performance Views
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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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Data Dictionary and Dynamic Performance Views
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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
htt // h bl t
1. Determine what datafile and tablespaces make up
the database
2. Determine the location of all the controlfile copies
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