If you use Oracle Data Guard, you can connect to one of the standby databases for read-only access. This allows you to move some of the load off your primary database for such operations as accessing data through a map service or including a query-only, sync-enabled feature service for reference purposes in a map you take offline.
Connect to the standby database as you normally would connect to any Oracle database from ArcGIS.
Be aware of the following when you connect to a read-only database:
- When you select (or a tool or process you run selects) more than 100 features in ArcMap, 1000 features in ArcGIS Pro or a feature service, a table is created in the geodatabase to cache information. This table cannot be created in a read-only database, so the selection will fail with the message database open for read-only access.
- If your map contains data from a read-only database, publishing an editable feature service will not fail but you won't be able to edit the resultant feature service.
- You must reconnect if a failover occurs and access to the Oracle Data Guard database is interrupted while you are connected to the database from ArcMap or ArcGIS Pro.
ArcGIS Server web services automatically resume the connection once the database is available.