OLE DB provider "OraOLEDB.Oracle" for linked server "TEST" returned message "ORA-01033: ORACLE initialization or shutdown in progress". (Microsoft SQL Server, Error: 7303)

TITLE: Microsoft SQL Server Management Studio
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The test connection to the linked server failed.

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ADDITIONAL INFORMATION:

An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)

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Cannot initialize the data source object of OLE DB provider "OraOLEDB.Oracle" for linked server "TEST".
OLE DB provider "OraOLEDB.Oracle" for linked server "TEST" returned message "ORA-01033: ORACLE initialization or shutdown in progress". (Microsoft SQL Server, Error: 7303)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&ProdVer=12.00.4237&EvtSrc=MSSQLServer&EvtID=7303&LinkId=20476

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BUTTONS:

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Installed Oracle client and Oracle provider ( https://sqlserverrandoms.blogspot.com/2018/03/installing-oracle-provider-for-oledb-in.html) and still getting the above error.

Reviewed lot of blogs, verified the registry and found everything looks good. Finally a reboot of server fixed this issue and able to create the Oracle linked server.

Try this work around if you see the same issue.