When multi-threaded servers are implemented, multiple Oracle clients share a smaller number of server processes. This can save memory and, in some cases, improve performance. If the number of shared servers is too small, however, client sessions may queue for an available server. Response time and throughput may suffer dramatically.
A similar problem can occur if there are insufficient dispatchers.
If Spotlight on Oracle detects a bottleneck in the Shared servers or dispatchers, then an alarm (such as the Multi-threaded Server Alarm) becomes current on the appropriate component within the Server Processes Panel.
If the alarms persist, you should alter the setting for MAX_DISPATCHERS or MAX_SHARED_SERVERS to ensure that sufficient processes are available for your workload. You could also consider using dedicated servers.