Oracle Database Startup and Shutdown Procedure
Introduction:
when the database before started there are four modes of startup and shutdown modes to open a database
Nomount State:
In Nomount state when the controlfile is to ready to open,Redologfiles and database files are closed and are not accessebile ,the oracle instance is available but some of the v$ views (dynamic performance views)are available during this Nomount state
Database may be brought to this state to perform some operation like
Creating Database
Recreating control file
eg: v$session,v$database,v$instance etc
Mount State:
In Mount state after the control file is opened and existence of all the database files and redolog files is to be verified to start up the database open
Database may be brought to this state to perform operations like
Backup
Recovery of the system crash or undo datafiles
change the database to archive log mode (when you query select name ,open_mode from v$database we will get the database is mounted)
Four Modes - -->shutdown Instance
1. shutdown normal
2. shutdown transactional
3. shutdown immediate
4. shutdown abort
1. shutdown normal
No new connections can be established
Will wait till users disconnect.
Changes are written to disk
No recovery required.
BG processes terminates and memory freed.
sql>shutdown
2. Shutdown transactional
sql>shutdown transaction
No new connections
will wait till users complete the transaction.
Changes writes in to datafiles.
no recovery is required
BG processes terminates and memory freed.
3. Shutdown immediate ( best Practice)
sql>shutdown immediate
sql>shut immediate
no new connections
Will not wait users disconnect/complete transaction
Changes written in to datafiles
uncommitted changes are rollbacked.
bg terminated and memory freed
no recovery required
4. shutdown abort
sql>shutdown abort
If database not responds then will do abort.
committed Changes will not write in to datafiles
Does need instance recovery by smon while instance startup.
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