> ## Documentation Index > Fetch the complete documentation index at: https://docs.bytebase.com/llms.txt > Use this file to discover all available pages before exploring further. # Instance > Understand how an Instance represents a database server or service in Bytebase. A Bytebase **Instance** represents a database server or service registered in a workspace or project. It stores the database engine, network endpoint, and authentication settings Bytebase uses to discover databases, synchronize their schema metadata, and execute authorized SQL. For example, the built-in PostgreSQL **Sample Project Instance** hosts `hr_test`. A separately registered shared PostgreSQL instance could host both `hr_test` and `payroll_test`. An instance serves a similar purpose to a saved connection in a database client, but also has a scope, environment, and synchronized database metadata. Read-only connections can be configured within the same instance. ## Instance versus Database An **Instance** identifies the server or service and how Bytebase accesses it. A **Database** identifies a database within that instance to inspect, query, or change. One instance can expose several databases; each database belongs to that instance. In the example above, select `Sample Project Instance` to manage the server's connection settings and database discovery. Select `hr_test` to inspect its schema or propose a change to its tables. ## What Instance means for each engine Bytebase uses **Instance** and **Database** consistently in the UI, but the corresponding native objects differ: | Engine | Bytebase Instance | Bytebase Database | | -------------- | ----------------------------------------------------------- | ---------------------------------------------------------------- | | **PostgreSQL** | PostgreSQL server or cluster | Native database containing schemas such as `public`, then tables | | **MySQL** | MySQL server | Native database, also called a schema, containing tables | | **SQL Server** | SQL Server instance or managed service | Native database containing schemas such as `dbo`, then tables | | **Oracle** | Oracle server or service addressed by a service name or SID | User-owned schema containing tables and other objects | For Oracle, a service name or SID selects the connection destination. A Bytebase database selects an Oracle schema, not a CDB or PDB. ## Workspace and project instances Instances have one of two scopes, chosen at registration: * **Workspace instance:** managed at workspace level; its databases can belong to different projects. * **Project instance:** belongs to one project, as do all of its databases. The scope cannot be changed later. A project's **Databases** page can show databases from both kinds of instance. Its **Instances** page shows only the instances it owns. Use a workspace instance when a central team manages a shared server and assigns its databases to different projects. Use a project instance when one project should manage the server and all its databases. A project-instance database cannot be transferred to another project independently. A workspace instance hosts databases assigned to different projects; a project instance and all its databases belong to one project ## How an instance is created Register an existing server or service; connecting an instance does not provision infrastructure. Workspace Admins and Workspace DBAs register workspace instances under workspace **Instances**. Project Owners register project instances under their project's **Instances** page. Custom roles can grant the same permissions. Click **Connect instance**, select an engine and environment, enter connection details, test, and save. Bytebase discovers visible databases, filtered by **Sync Databases**. Project-instance databases join the owning project; workspace-instance databases may need assignment. ## Use an instance Open the instance from the appropriate **Instances** page to inspect its discovered databases, synchronization status, and connection settings. You can also follow the **Instance** link from a database's detail page if your role permits it. Bytebase can discover only databases visible to the configured database account and allowed by **Sync Databases**. If an expected database is missing, the instance operator should check those settings and the latest synchronization result. Connection failures require checking reachability from Bytebase, credentials, TLS, and engine-specific settings. Managing an instance requires instance permissions. A member can have permission to query a database without permission to administer its instance. See [Database](/concepts/database) for target selection and [instance connection settings](/get-started/connect/overview) for setup.