DBA

Starting up a database (Nomount) :-

* When starting the database, you select the states in which it starts.

• Usually start an instance without mounting a database only during database creation or the recreation of control-files.

sql>Startup nomount

*Starting an instance include following tasks,

• Reading the initializtion files
• Allocating the SGA
• Starting the background processes
• Opening the alertSID.log file and the trace files.
• The database must be named with the db_name parameter.

Starting up a database (Mount) :-

* The database must be mounted but not open during the following tasks,

• Renaming datafiles
• Enabling and disabling redo log archive options
• Performing full database recovery
• Locating and opening the control file specified initializtion parameters file.
• Reading the control files to obtain the name and status of the redo log files and datafiles.

Starting up a database (Open) :-

* An instance started and database mounted and then datbase opened. During database open ,the user can be attempt to open database and performing.

*During the database open following tasks,

• Datafiles and ONline redolog files are Available

Note :- When you open the database, a datafiles and online redo log file not avilable ,the oracle returns error. Mean time database needs recovery options.

*** If necessary,System Monitor background process (SMON) initiates instance recovery.

Startup Command :-

To startup an instance, use the following commands

• Startup [force] [restrict] [pfile=filename] [open [recover] [database] Mount Nomount ]

Note :- This is not the Complex syntax.

• Force ---> aborting the running instance before performing a startup
• Restrict ---> Enables only users with restricted session privilege to access the database
• Recover ---> can be media recovery when the database starts

**** Attempting to open Oracle utilities without start the service, Oracle returns a error Ora-12547 --TNS

The Alter Database Command :-

* Chang the states of the database from Nomount ot Mount stage,

sql> alter database db01 mount;

* Open the database read only mode

sql> alter database db01 open read only;

Alter database db01 open [read only read write]

where

• Read Write ---> Opens the database read write mode so users can generate redo logs.
• Read Only ----> Restrict users to read only transactions,preventing them from generating Redo log information.

Restrict Command :-

sql>startup restrict;

* Use the Alter system command in restriction mode,

sql> alter system enable restricted session;

**** When you perform struture maintanice or database export or import. The database can be restricted session so that it is available only to the restricted session privilige users.

Alter system [enable disable ] restricted session;

• Enable ---> who have restircted privilige users
• Disable ----> users who do not have the priviliges also log on.

Terminate Session :-

* After placing an instance in resticted mode, you may want to kill all current user sessions before performing administrative tasks.

• Alter system kill session 'integer1,integer 2'

Where

• Integer 1 ----> Value of the column in the v$session view
• Integer 2 ----> value of the serail# in the v$session view

***** http://www.oracle-base.com/articles/misc/KillingOracleSessions.php

Efects of Terminating a Session :-

* Pmon perform following tasks,

• Roll back the users current transaction
• Release all currently held table or rows
• Free all resources currently reserved by the user

Opening database in Read Only Mode :-

• Executes query
• Execute disk sort using locally managed tablespace
• Take datafiles offline and Online ,.Not tablespace
• Perform recovery offlines of datafile and tablespace.