0 Startup and Shutdown modes in oracle database

Startup and Shutdown modes

• The parameter file contains the information of parameters which controls the database
• The default space or location where the parameter file resides is ORACLE_HOME/dbs
• The satrtup mount means creating (SGA)System global Area and starting the background process
• Before we go to the startup mount state we must edit the init.ora parameter file and copy it into oracle_SID
• If one datafile is not synchronizing with the database then the control file throws an error.we want to restore it and then only we can startup the database.An now end users can connect to the database

There are different shutdown commands: there are 4 types of shutdown commands mainly

• shutdown normal(graceful shutdown)
• shutdown immediate
• shutdown transactional
• shutdown abort

Let us discuss in detail about those four things

Normal Shutdown

This is a time consuming and safest shutdown.Because here if there are three users working accessing a database and at now dba sends the shutdown normal option.then it wont access the new user enter into the database to access the database.

   And the system wait until all the clients are accessing the database is logged out.Thet means the user who are accessing the database can access the database upto any time.But once he logged out he do not yet login.i.e,the user can start new transaction and he executes his current session.and the dbwr synchronise the datafiles.And it will dismount the database whenever all the clients have been loggedout.Hence it goes with the graceful shutdown.So that there is no requirment of instance crash recovery.

Immediate Shutdown

In the immediate shutdown no new connection for the user establisshes.And the current transaction must be rolledback.And it should immediately close the current session.And here we can synchronize the  data memory to datafiles.we can dismount the database and we can gracefully shutdown and ICR was not triggered.

Transactional Shutdown

Here also no new connection is provided.The system waits until the current transaction is completed.And then immediately closes the current session.Synhronization of data memory to the datafiles is happened.we can dismount the database and also we can perform the graceful shutdown and we have no need of instance crash recovery

Abort Shutdown

The very immediate shutdown is an abort and either of 3 mention above are not worked so,then generally a database administrator will go through this shutdown.Here if a database administrator will go through this shutdown.then immediately sga directly will be released and generally it was not a gracefull shutdown so that instance crash recover is needed