Oracle DB Instance State

1, has been started/not loaded (Nomount). Launches the instance, but does not mount the database.
This mode is used to recreate the control file, restore the control file, or recreate the database.
2, Loaded (Mount). Mount the database without opening the database.
This mode is used to change the archive mode of the database or to perform recovery operations to recover data files.
3. Turn on (open).
4, close.

To close the database:
1. Shutdown normal
Oracle no longer accepts new connections, and the database waits until the user who is currently connected to the database disconnects and then shuts down the DB instance.
2, Shutdown immediate
The database will not allow a new connection to be established, nor is it allowed to start a new transaction. All uncommitted transactions are performed with a rollback operation.
3, Shutdown transactional
The database will not allow a new connection to be established, nor is it allowed to start a new transaction. Disconnect all connected users after the transaction is complete, and then close the database.
4, Shutdown abort
New connections are not allowed, and new transactions are not allowed to start. All executing client SQL statements are immediately aborted, no committed transactions are rolled back, and the connection to all online users is immediately severed.

Restricted mode Startup database: startup restrict
1. Perform data import and export
2. Use Sql*loader to extract data from external databases
3, need to temporarily deny ordinary users access to the database
4. Perform a database migration or upgrade operation

(quiesce) Pause database:
In this state, only users with DBA authority are allowed to execute transactions, queries, and UPDATE statements.
1. Switching the database to a paused state
alter system QUIESCE restricted;
2. Return to normal from standstill
alter system UNQUIESCE;
3. View instance activity status
Sql> select Active_state from V$instance;

Active_st
---------
NORMAL

V$blocking_quiesce. Sid=v$session. Sid View session information blocked by a paused operation
Sql> desc V$BLOCKING_QUIESCE
Name Null? Type
---------- -------- ----------------------------
SID number

Sql> desc v$session
Name Null? Type
----------------------------------------- -------- ----------------------------
Saddr RAW (8)
SID number
serial# number
Audsid number
Paddr RAW (8)
user# number
USERNAME VARCHAR2 (30)
COMMAND number

Suspend (suspend) database:
All I/O to the data file and control file is aborted, and new access to the database is switched to a paused state.
1. Suspending the database
alter system suspend;
2, return to normal
alter system resume;
3. View database Status
Sql> select Database_status from V$instance;

Database_status
-----------------
ACTIVE

Oracle DB Instance State