Key to understanding a situation similar to Figure 2-18 is recognizing the single underlying wait event for the Net+Client queue time category is SQL*Net message from client. When a server process is waiting to hear from its client process, it will post the wait event SQL*Net message from client. A server process does not know if the user associated with the client process is waiting for the client process to complete, if there is a problem with the network, or if the user is taking a coffee break. All the server process knows is that it has nothing to do and is programmed to scream, SQL*Net message from client! In a very real sense, the server process is waiting for a message via SQL*Net from its client process. So, in this case, the wait event is actually very descriptive.

Figure 2-18. Report output from a session-level ORTA based on a single and identifiable Oracle session. The session is waiting primarily for information from the client process, which leads the analyst to suspect issues with the client program or the network communication between the client and server process.

Here's the strange part: both the application user and the Oracle server process are waiting! That is very unusual indeed. If the user has executed a command and is waiting for the command to complete, while at the same time, the associated Oracle server process is waiting to hear from its client process, then there is problem between the two. The two broad problem areas are the network and the client process.