I have been trying to delete multiple campaigns from Eloqua at a time using Postman. But I am not able to do. I don't see reference in the tool as well http://docs.oracle.com/cloud/latest/marketingcs_gs/OMCAB/index.html#Developers/RESTAPI/REST-API.htm%3FTocPath%3D%2520Application%2520API%7C_____0.
Please let me know if deleting the multiple campaigns is possible.
It is not possible.
The link you provided mentions it's outdated, and a redirection link was available: http://docs.oracle.com/cloud/latest/marketingcs_gs/OMCAC/rest-endpoints.html
Have a look at all the DELETE methods over there, and you will see that there is no provision for sending more than one id
at a time.
Edit: You say you are using Postman. It is possible to perform repetitive tasks (like deleting mulitple campaigns) with different parameters each time by using Collections.
Edit 2:
Type your url with the id as a variable, e.g.: xyz.com/delete/{id}
And send all the id values as a JSON or CSV file. They have given a sample JSON, you would simply have to provide your ids inside an array, e.g.:
[
{"id":1},
{"id":2},
{"id":3}
]