Quick Answer: What To Do If Database Is Down?

What is the difference between an instance and a database?

While the database itself includes all the application data and metadata stored in physical files on a server, an instance is a combination of the software and memory used to access that data.

An Oracle instance can access only one database at a time, while an Oracle database can be accessed by multiple instances..

What is idle instance in Oracle?

Actually, Connected to an idle instance is a message rather than an error, it indicates that the database you entered is idle, stopped or shutdown. It’s pretty normal if your database instance is not started up, you can just start the Oracle database instance up and check the open status.

Which files must be synchronized for a database to open?

SMON will synchronize all files by instance recovery after opening the database. 5. A. These are the files that make up a database, and all must be synchronized if the database is to open.

What is Crash Recovery in Database?

Crash recovery is the process by which the database is moved back to a consistent and usable state. … This is done by rolling back incomplete transactions and completing committed transactions that were still in memory when the crash occurred (Figure 1).

What are the different types of failure in DBMS?

Distributed DBMS – Failure & CommitOperating system failure.Main memory crash.Transaction failure or abortion.System generated error like integer overflow or divide-by-zero error.Failure of supporting software.Power failure.

Why is it so long to shut down immediate?

Shutdown immediate can take long time to complete (appear to be hung) because of three reasons: 1. Uncommitted transactions are being rolled back.

What causes a database to crash?

File Permission and Corruptions – A great number of database crashes are caused by file permission issues, corrupted data, and index files. … The database server tries to read/write from an already crashed and corrupted data/index file. 4.) A defective piece of hardware, such as I/O corrupting a data/index file.

How do you check database is mounted or not?

SELECT open_mode FROM v$database; If the value is: ‘MOUNTED’, your database is mounted. ‘READ WRITE’, then you can assume it’s been activated.

What is DB Instance Oracle?

Introduction to the Oracle Database Instance. A database instance is a set of memory structures that manage database files. A database is a set of physical files on disk created by the CREATE DATABASE statement. The instance manages its associated data and serves the users of the database.

How can I tell if my database is in open mode?

Log in to the database server as the oracle user (Oracle 11g server installation user). Run the sqlplus “/as sysdba” command to connect to the database. Run the select open_mode from v$database; command to check the database status.

Which view will list all tables in the database?

The easiest way to see all tables in the database is to query the all_tables view: SELECT owner, table_name FROM all_tables; This will show the owner (the user) and the name of the table. You don’t need any special privileges to see this view, but it only shows tables that are accessible to you.

How do you mount a database?

To mount the database, the instance finds the database control files and opens them. Control files are specified in the CONTROL_FILES initialization parameter in the parameter file used to start the instance. Oracle then reads the control files to get the names of the database’s datafiles and redo log files.

How do I shutdown an Oracle instance?

To start or shut down Oracle Database:Go to your Oracle Database server.Start SQL*Plus at the command prompt: C:\> sqlplus /NOLOG.Connect to Oracle Database with username SYSDBA: SQL> CONNECT / AS SYSDBA.To start a database, enter: SQL> STARTUP [PFILE=path\filename] … To stop a database, enter: SQL> SHUTDOWN [mode]

How do I run a database using Spfile?

In the NOMOUNT stage, Oracle carries the following steps: First, search for a server parameter file in the default location. You can override the default behavior by using the SPFILE or PFILE parameters in the STARTUP command. Next, read the parameter file to get the values of the initialization parameters.

How do I change database status mounted to open?

To open a mounted database, use the ALTER DATABASE statement with the OPEN clause: ALTER DATABASE OPEN; After executing this statement, any valid Oracle Database user with the CREATE SESSION system privilege can connect to the database.