ALTER DATABASE [Database_name] SET ENABLE_BROKER equivalent statement in ORACLE

There isn't a one-to-one equivalence between the SQL Server broker and an Oracle process.

What are you trying to accomplish?  Perhaps we can help with a work-around.

Can you explain what that statement does in SQL Server?  Some of us don't know much about SQL Server, so for me at least, seeing that particular SQL Server command doesn't tell me anything about what it actually does.

It is to enable notification. Please find the below link

https://blog.sqlauthority.com/2009/09/21/sql-server-intorduction-to-service-broker-and-sample-script/

As I said, there is no equivalency.  Even if you could enable something similar, Oracle doesn't send/handle/support notifications like SQL Server does.

OK, that helps.  I agree with what Kent Olsen said: oracle and SQL Server do not do everything exactly the same way.  Oracle has “database links” to connect to other databases.  And Oracle supports queues, if necessary, to help with sending transactions to other systems.

But, depending on exactly what your other “database” is, you may not need either a database link or a queue.  You may only need a grant, if the other “database” is simply another schema in the same Oracle database.

In my Googling on this, specifically SIGNALR, it appears the Oracle comparable might be: Change Notification
http://www.oracle.com/webfolder/technetwork/tutorials/obe/db/dotnet/changenotification/ChangeNotification.htm

As you can probably tell from the previous comments, there are very few Experts here that are interchangeable between Oracle and SQL Server.  From everything Ive read, you really cannot do direct ports between the systems and should NEVER try.

dbms_alert
https://docs.oracle.com/database/121/ARPLS/d_alert.htm#ARPLS351
a very simple, but not very flexible, system to get alerts after subscribing
dunno in asp.net, but we open a separate thread subscribing to certain messages
it gives a timeout or a message

as dbms_alert is not very flexible, we are investigating oracle advanced queuing
https://docs.oracle.com/database/121/ADQUE/aq_intro.htm#ADQUE0100
it can be used as a notification system, but also requires subscribing