Hi Team,

Can you please explain:
1) The use of Alternate Servers in the SQL DataSource Object.
2) We already configure the service ID , host , port in the Main page, then on what conditions/scenario the flow goes to the alternative servers configured in the another tab.

Thanks

My understanding is that "AlternateServers" applies to only Oracle for HA support of a RAC. In this configuration, you define the "service name", not the SID. See the following topic and its child topic.
> https://www.ibm.com/docs/en/datapower-gateway/10.5.x?topic=sources-creating-oracle-data-source

But I am not clear still on when the Alternate servers are being used.

I mean 
We already configure the service ID , host , port in the Main page, then on what conditions/scenario the flow goes to the alternative servers configured in the another tab.

I think you need to talk with your Oracle DBA for the way that Oracle (and other data sources) work for high availability and failure is based on how the "service" is defined and the "management server" to contact to know which actual server to connect to that has this service.

When you configure the Oracle data source, you specify the "service name" (that represents the group of addresses) and then an the ancillary servers you generally specify the "SID" (that is a specific server instance). In other words, imagine the "service name" as being a business office and each "SID" is a specific room in that office.  In other words, based on how you "address" the delivery, it'll either go to the business office (service name) and they'll handle sending it to the specific room (SID) or you can send "address" the delivery to a specific room (SID).

With this example, as part of the base configuration, you need to provide the connection details to the "service name", not SID. Then for the ancillary servers, you specify the connectin details for each SID. When correctly configured, you'll have created a valid "tnsnames.ora file".