Startup shutdown modes oracle database
In this post, we will discuss Startup and shutdown modes of Oracle database.
The startup modes include startup open, startup mount, startup nomount and
shutdown modes include shutdown abort, shutdown transactional, shutdown normal, shutdown immediate.
Startup and shutdown modes oracle database
Startup modes
nomount state:
This stage is only used when first creating a database or when it is necessary to recreate a database’s control files. Startup nomount includes the following tasks.
- Read the spfileSID.ora or spfile.ora or initSID.ora.
- Allocate the SGA.
- Startup the background processes.
- Open a log file named alert_SID.log and any trace files specified in the initialization parameter file.
In a nomount state, Oracle scans the content of the control file for the physical locations of datafiles and redo log files.
mount state:
This is nothing but associating an instance with the database.
Mount state is used to perform some maintenance activities like configuring the database in archive log mode, flashback mode and performing database recovery.
the mount state is also used by the dba to create a standby control file for configuring a standby database using data guard.
open state:
In open state oracle checks for the existence of datafiles and redo log files and it also performs a check for synchronization of SCN number.
Also, read Oracle database startup modes activity guide.
Database shutdown modes
They are of four types
- Shutdown normal or shutdown
- Shutdown transactional
- Shutdown immediate
- Shutdown abort
Shutdown Normal:
This is graceful shutdown.
- No new connections will be allowed.
- The server waits for all users to disconnect before completing the shutdown.
- Database and redo buffers are written to disk.
- The SGA memory allocation is released and background processes terminate.
- The database is closed and dismounted.
Shutdown Transactional:
This prevents client computers from losing work.
- No new connections will be allowed.
- No connected client can start a new transaction.
- Clients are disconnected as soon as the current transaction ends.
- Shutdown proceeds when all transactions are finished.
Shutdown Immediate:
This can cause client computers to lose work.
- No new connections are allowed.
- Connected clients are disconnected and SQL statements in a process are not completed.
- Oracle rolls back active transactions.
- Oracle closes/dismounts the database.
Shutdown Abort:
This is used if the normal or transactional or immediate options fail. This is the LEAST favored option because the next startup will require instance recovery and you CANNOT backup a database that has been shut down with the ABORT option.
- Current SQL statements are immediately terminated.
- Users are disconnected.
- Database and redo buffers are NOT written to disk.
- Uncommitted transactions are NOT rolled back.
- The Instance is terminated without closing files.
- The database is NOT closed or dismounted.
- Database recovery by SMON must occur on the next startup.
Also, read The activity post for the Startup and shutdown modes of Oracle database.
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