Explanation:
When a client machine initiates a shared server connection to the database in Oracle9i, the listener uses the direct handoff whenever possible. This connection process requires fewer network calls and, accordingly, less overhead.
When the listener receives the request from the client for a shared server connection, it locates the address of the least loaded dispatcher process. In previous versions, the next step would have been to pass this address back to the client for the client to contact the dispatcher again over the network. Instead, in Oracle9i’s direct handoff method, the listener hands the connection request to the dispatcher. The dispatcher communicates directly with the client to establish a connection without the need for the additional network calls that were required in previous versions.
Incorrect Answers:
1: The initial request from the client to the listener is not eliminated.
2: Messages between the dispatcher and the shared server background processes are used in Oracle9i also as in previous versions.
4: Round-trip messages between the listener and the shared server background processes are used in Oracle9i as in previous versions of Oracle.
Reference:
OCP Oracle9i Database: New Features for Administrators, Daniel Benjamin, p. 144-152
Chapter 3: Manageability Enhancements
Oracle 9i New Features, Robert Freeman, p. 59-60
Chapter 2: Oracle9i Architecture Changes

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