It's a broad question so this is a broad answer...
Your solution will depend on the interfaces between your IVR system and CRM system. If your IVR can consumer a web service and your CRM system exposes itself via a web service then that would be a great solution. Your integration points will need to be common on both ends. Given that you can't keep the caller on hold for too many seconds, while you retrive their information from the CRM system, a web service inteface is relatively responsive and is a good choice. Respone time is going to depend on a number of factors -- how you consume the service (e.g. Axis), the complexity of the call (does the CRM system have to do a lot of work to do before it returns the response), network latency, etc.
Another option is to go direct to the Oracle database, but typically you then lose the business rules enforcement provided by the CRM system and have to write them into the IVR code.
More details would help narrow the solution.
