Question - Can one database have multiple instances?

Answered by: Scott Cox  |  Category: General  |  Last Updated: 24-06-2022  |  Views: 1320  |  Total Questions: 14

Using Oracle's Parallel Server (OPS), which was renamed to Oracle's Real Application Clusters (RAC), you can have multiple instances connected to the same database. Without OPS or RAC, you must have one instance for each database if you want to access data in that database. In SQL Server Replication, you can have both of your server available and you can even update both copy of your database and have them synchronized on both servers. Otherwise, it's a simple no. Each instance wants to use the files exclusively. 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. As long as all your database instances are on the same server you can build as many as you want without paying any more. Each database so created has a different name. To access them it's simply a matter of using a tnsnames. ora file with different entries for each instance on the server. 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.

https://beginnersbook.com/2015/04/instance-and-schema-in-dbms/

Definition of instance: The data stored in database at a particular moment of time is called instance of database. Database schema defines the variable declarations in tables that belong to a particular database; the value of these variables at a moment of time is called the instance of that database.

https://support.solarwinds.com/SuccessCenter/s/article/How-to-identify-your-SQL-Server-version-and-e

Identify the SQL Server instance name Open a command prompt window. Execute: services. msc. Scroll down to entries beginning with SQL. Locate an entry for each installed named SQL Server (instancename). The value in parenthesis is your instance name.

https://www.quora.com/What-is-the-difference-between-instance-name-and-database-name

A db instance is an install of a database server. A db instance is an install of a database server. A db instance can contain many databases.

https://www.techopedia.com/definition/32149/server-instance

A server instance is a collection of SQL Server databases which are run by a solitary SQL Server service or instance. The details of each server instance can be viewed on the service console which can be web-based or command-line based.

https://docs.oracle.com/cd/E19159-01/819-3671/geolm/index.html

The server instance is a single Java EE compatible Java Virtual Machine hosting an Application Server on a single node. Each server instance has a unique name in the domain. The application server instance is a building block in the clustering, load balancing, and session persistence features of the Application Server.

http://www.adp-gmbh.ch/ora/misc/database_vs_instance.html

Difference between a database and an instance [Oracle] The database is the set of files where application data (the reason for a database) and meta data is stored. An instance is the software (and memory) that Oracle uses to manipulate the data in the database.

http://www.differencebetween.net/technology/difference-between-a-server-and-database/

Difference between a Server and Database. Generally, a Server is a high-end network computer managing connected devices (“clients”) and their access to multiple applications as a central resource, whereas a Database is a repository that supports an application's back-end data processing.

https://stackoverflow.com/questions/3861723/what-is-mean-by-server-instance-in-mssqlserver-2005

A server is a (physical or virtual) machine hosting SQL Server software. An instance is a collection of SQL Server databases run by a single SQL Server service, ahem, instance. You can view each separate instance you're running in your service console. You're meant to use instances to partition data and policies.

https://www.pearsonitcertification.com/articles/article.aspx?p=350920&seqNum=5

Create a Database Manually Step 1: Decide on Your Instance's System Identifier (SID) Step 2: Create the Initialization Parameter File. Step 3: Connect to and Start the Instance. Step 4: Issue the CREATE DATABASE Statement. Step 5: Run Scripts to Build Data Dictionary Views. Step 6: Run Scripts to Install Additional Options.

https://support.office.com/en-us/article/create-a-new-database-32a1ea1c-a155-43d6-aa00-f08cd1a8f01e

Create a blank database On the File tab, click New, and then click Blank Database. Type a file name in the File Name box. Click Create. Begin typing to add data, or you can paste data from another source, as described in the section Copy data from another source into an Access table.

https://docs.oracle.com/cd/F49540_01/DOC/server.815/a67772/create.htm

To Create a New Database and Make It Available for System Use Back up any existing databases. Create parameter files. Edit new parameter files. Check the instance identifier for your system. Start SQL*Plus and connect to Oracle as SYSDBA. Start an instance. Create the database. Back up the database.

https://www.dummies.com/programming/databases/how-to-use-the-database-configuration-assistant-dbca-t

The following steps take you through the process: Log in as the Oracle software owner. Go to a command prompt. Type dbca. You see a splash screen and another screen with options. Select the Create a Database option. Select the Advanced option. Click Next. Select the Custom Database option. Click Next.

https://docs.oracle.com/cd/E18283_01/appdev.112/e10766/tdddg_connecting.htm

To connect to Oracle Database from SQL Developer: Access the menu from which you can select SQL Developer: Select Oracle - ORACLE_HOME. Select Application Development. Select SQL Developer. In the navigation frame of the window, click Connections. In the Connections pane, click the icon New Connection.

https://www.orafaq.com/wiki/ORACLE_SID

ORACLE SID. From Oracle FAQ. The Oracle System ID (SID) is used to uniquely identify a particular database on a system. For this reason, one cannot have more than one database with the same SID on a computer system. When using RAC, all instances belonging to the same database must have unique SID's.